Magnetic domain wall movement element and magnetic recording array

The present invention relates to a magnetic domain wall movement element and a magnetic recording array. Priority is claimed on Japanese Patent Application No. 2019-030434, filed on Feb. 22, 2019 and Japanese Patent Application No. 2020-012694, filed on Jan. 29, 2020, the contents of which are incorporated herein by reference.

Attention has been focused on next-generation non-volatile memories that will replace flash memories or the like for which the limit of miniaturization has been reached. For example, magnetoresistive random access memories (MRAMs), resistance random access memories (ReRAMs), phase change random access memories (PCRAMs), and the like are known as next-generation non-volatile memories.

In MRAMs, a change in resistance value caused due to change in magnetization direction is used for data recording. In order to increase the capacity of recording memories, the miniaturization of each of elements constituting a memory and increasing the number of recording bits per element constituting the memory are being researched.

Patent Document 1 describes a magnetoresistive element in which movement of a magnetic domain wall is used. The magnetoresistive element described in Patent Document 1 has information recorded in an analog manner in accordance with a position of a magnetic domain wall. In the magnetoresistive element described in Patent Document 1, a range in which a magnetic domain wall can move is controlled using a magnetization fixed section.

[Patent Document 1] Japanese Patent No. 5598697

A resistance value changes in accordance with a difference between relative angles of magnetizations of two ferromagnetic materials having a nonmagnetic layer disposed therebetween. A magnetic domain wall movement element stores data on the basis of the resistance value. In a magnetic domain wall movement element, in order to prevent a domain wall from disappearing, a magnetization fixed section is provided in the magnetic recording layer in which a magnetic domain wall moves in some cases. Furthermore, in order to increase a degree of integration of a plurality of magnetic domain wall movement elements, a reference layer serving as a reference for resistance change is laminated on one surface of the magnetic recording layer including the magnetization fixed section in some cases. The magnetization fixed section has a fixed direction of magnetization and a relative angle between a magnetization of the magnetization fixed section and a magnetization of the reference layer does not change. Therefore, the magnetization fixed section does not cause a change in resistance value of the magnetic domain wall movement element and a range of change in resistance decreases by an extent corresponding an overlap between a magnetization fixed layer and the reference layer when viewed in a plan view. If a range of change in resistance value increases, for example, it is possible to prevent data recorded by the magnetic domain wall movement element from varying due to noise.

The present invention was made in view of the above-described problems and provides a magnetic domain wall movement type magnetic recording element and a magnetic memory which have a wide range of change in resistance and are stable.

(1) A magnetic domain wall movement element according to a first aspect includes: a first ferromagnetic layer; a magnetic recording layer located in a first direction with respect to the first ferromagnetic layer and extending in a second direction; a nonmagnetic layer located between the first ferromagnetic layer and the magnetic recording layer; and a first electrode and a second electrode which are located on a side of the magnetic recording layer opposite to the nonmagnetic layer, and each of the first electrode and the second electrode being configured to overlap with a part of the magnetic recording layer in the first direction, wherein the first electrode includes a magnetic material whose magnetization is oriented in a direction different from a direction of magnetization of the first ferromagnetic layer, the magnetic recording layer includes: a first region which overlaps with the first electrode and the first ferromagnetic layer in the first direction; a second region which overlaps with the second electrode and the first ferromagnetic layer in the first direction; and a third region which is located between the first region and the second region, an area of a first section in the first region facing the first electrode is larger than an area of a second section in the second region facing the second electrode, and the first ferromagnetic layer overlaps with a part of the first electrode and a part of the second electrode in the first direction.

(2) In the magnetic domain wall movement element according to the aspect, the second electrode may include a magnetic material whose magnetization is oriented in the same direction as the direction of magnetization of the first ferromagnetic layer.

(3) The magnetic domain wall movement element according to the aspect further includes: a substrate, wherein the first ferromagnetic layer may be located closer to the substrate than the magnetic recording layer.

(4) The magnetic domain wall movement element according to the aspect further includes: an insulating layer configured to cover the third region of the magnetic recording layer.

(5) The magnetic domain wall movement element according to the aspect further includes: a substrate, wherein the first ferromagnetic layer may be located farther from the substrate than the magnetic recording layer.

(6) In the magnetic domain wall movement element according to the aspect, a lateral surface of the magnetic recording layer in the second direction may be inclined with respect to the first direction.

(7) In the magnetic domain wall movement element according to the aspect, the first electrode may have a first inclined section inclined with respect to the first direction.

(8) On a virtual cross-section passing through a center of the magnetic recording layer in the magnetic domain wall movement element according to the aspect in a third direction orthogonal to the first direction and the second direction and extending in the first direction and the second direction, the first electrode may have a first lateral surface and a second lateral surface located closer to the second electrode than the first lateral surface, and the first lateral surface may have a portion having an inclination angle larger than an inclination angle with respect to the first direction of the second lateral surface.

(9) On a virtual cross-section passing through a center of the magnetic recording layer in the magnetic domain wall movement element according to the aspect in the third direction orthogonal to the first direction and the second direction and extending in the first direction and the second direction, the first electrode may have a first lateral surface and a second lateral surface located closer to the second electrode than the first lateral surface, and the first lateral surface may have a portion in which an inclination thereof with respect to the first direction changes discontinuously.

(10) A magnetic recording array according to a second aspect may include: a plurality of the magnetic domain wall movement elements according to the aspect.

According to the magnetic domain wall movement element and the magnetic recording array according to the aspect, it is possible to increase a range of change in resistance.

FIG. 1 is a cross-sectional view of a semiconductor device according to a first embodiment.

FIG. 2 is a cross-sectional view of a storage element according to the first embodiment.

FIG. 3 is a plan view of the storage element according to the first embodiment.

FIG. 4 is a plan view of a first modification of the storage element of the semiconductor device according to the first embodiment.

FIG. 5 is a cross-sectional view of a second modification of the storage element of the semiconductor device according to the first embodiment.

FIG. 6 is a schematic cross-sectional view of a third modification of the storage element of the semiconductor device according to the first embodiment.

FIG. 7 is a schematic plan view of the third modification of the storage element of the semiconductor device according to the first embodiment.

FIG. 8 is a schematic cross-sectional view of a fourth modification of the storage element of the semiconductor device according to the first embodiment.

FIG. 9 is a schematic cross-sectional view of a fifth modification of the storage element according to the first embodiment.

FIG. 10 is a schematic cross-sectional view of a semiconductor device according to a second embodiment.

FIG. 11 is a schematic cross-sectional view of a storage element of the semiconductor device according to the second embodiment.

FIG. 12 is a schematic cross-sectional view of a sixth modification of the storage element of the semiconductor device according to the second embodiment.

FIG. 13 is a constitution diagram of a magnetic recording array according to a third embodiment.

This embodiment will be described in detail below with reference to the drawings as appropriate. In the drawings used in the following description, in order to make the characteristics of the present invention easy to understand, for convenience, characteristic portions may be illustrated in an enlarged manner in some cases and dimensional ratios or the like of constituent elements may be different from actual dimensional ratios in some cases. The materials, dimensions, and the like exemplified in the following description are merely examples and the present invention is not limited thereto and it is possible to appropriately change and implement the present invention with a range in which the effects of the present invention can be obtained.

First, directions will be defined. An x direction and a y direction are directions substantially parallel to one surface of a substrate 60 which will be described later. The x direction is a direction in which a magnetic recording layer 20 which will be described later extends. The x direction is an example of a second direction. The y direction is a direction orthogonal to the x direction. A z direction is a direction orthogonal to the x direction and the y direction. The z direction is an example of a first direction. Furthermore, the expression “extends in the x direction” in the specification means that, for example, a dimension in the x direction is larger than a minimum dimension among dimensions in the x direction, the y direction, and the z direction. The same applies to the case of extending in other directions.

First Embodiment

<Semiconductor Device>

FIG. 1 is a cross-sectional view of a semiconductor device according to a first embodiment. FIG. 1 is a cross section taken along an xz plane passing through a center of a width of a magnetic recording layer 20 in the y direction. A semiconductor device 200 includes a plurality of storage elements 100 and semiconductor elements (for example, transistors) connected to the storage elements 100 . FIG. 1 illustrates three transistors connected to the storage elements 100 , focusing on one of the storage elements 100 for convenience. The semiconductor device 200 includes a first ferromagnetic layer 10 , the magnetic recording layer 20 , a nonmagnetic layer 30 , a first electrode 40 , a second electrode 50 , the substrate 60 , a third electrode 70 , a plurality of insulating layers 80 , a plurality of conductive sections 90 , a first wiring Cm, a second wiring Wp, a third wiring Rp, a plurality of gate electrodes G 1 , G 2 , and G 3 , and a plurality of gate insulating films GI 1 , GI 2 , and GI 3 . The first ferromagnetic layer 10 , the magnetic recording layer 20 , the nonmagnetic layer 30 , the first electrode 40 , and the second electrode 50 are referred to as the storage element 100 . The storage element 100 is an example of a magnetic domain wall movement element. The semiconductor device 200 illustrated in FIG. 1 has a top pin structure in which the magnetic recording layer 20 is located closer to the substrate 60 than the first ferromagnetic layer 10 .

“Substrate, Gate Electrode, and Gate Insulating Film”

The substrate 60 is, for example, a semiconductor substrate. The substrate 60 includes a plurality of source regions S 1 , S 2 , and S 3 and a plurality of drain regions D 1 , D 2 , and D 3 . The plurality of source regions S 1 , S 2 , and S 3 and the plurality of drain regions D 1 , D 2 , and D 3 are regions having impurities doped in the substrate 60 . The source region S 1 , the drain region D 1 , the gate electrode G 1 , and the gate insulating film GI 1 serve as a first transistor Tr 1 . The source region S 2 , the drain region D 2 , the gate electrode G 2 , and the gate insulating film GI 2 serve as a second transistor Tr 2 . The source region S 3 , the drain region D 3 , the gate electrode G 3 , and the gate insulating film GI 3 serve as a third transistor Tr 3 .

“Insulating Layer”

The insulating layers 80 each are insulating layers which insulate between wirings of multilayer wirings and between elements. The insulating layer 80 electrically separates the substrate 60 , the first wiring Cm, the second wiring Wp, the third wiring Rp, and the storage element 100 except for the conductive sections 90 .

The same material as that used for a semiconductor device or the like can be used for the insulating layer 80 . The insulating layer 80 is made of, for example, silicon oxide (SiO x ), silicon nitride (SiN x ), silicon carbide (SiC), chromium nitride, silicon carbonitride (SiCN), silicon oxynitride (SiON), aluminum oxide (Al 2 O 3 ), zirconium oxide (ZrO x ), and the like.

“Wiring”

The first wiring Cm is a common wiring. The common wiring is a wiring used both at the time of writing data and at the time of reading data. The second wiring Wp is a write wiring. The write wiring is a wiring used at the time of writing data. The third wiring Rp is a read wiring. The read wiring is a wiring used at the time of reading data. If the first transistor Tr 1 and the third transistor Tr 3 are turned on, the second wiring Wp and the first wiring Cm are electrically connected and a write current flows through the storage element 100 . If the second transistor Tr 1 and the third transistor Tr 3 are turned on, the third wiring Wp and the first wiring Cm are electrically connected and a read current flows through the storage element 100 .

“Conductive Section”

Each of the conductive sections 90 electrically connects each of the first wiring Cm, the second wiring Wp, the third wiring Rp, and the storage element 100 to the substrate 60 . The conductive section 90 includes a material having conductivity. A conductive section 91 electrically connects the second wiring Wp to the source region S 1 of the first transistor Tr 1 . A conductive section 92 electrically connects the second electrode 50 to the drain region D 1 of the first transistor Tr 1 . A conductive section 93 electrically connects the third wiring Rp to the source region S 2 of the second transistor Tr 2 . A conductive section 94 electrically connects a wiring 71 to the drain region D 2 of the second transistor Tr 2 . A conductive section 95 electrically connects the first wiring Cm to the source region S 3 of the third transistor Tr 3 . A conductive section 96 electrically connects the first electrode 40 to the drain region D 3 of the third transistor Tr 3 . The conductive sections 91 , 92 , 93 , 94 , 95 , and 96 extend in the z direction.

“Third Electrode”

The third electrode 70 is an electrode configured to flow a read current through the storage element 100 . The third electrode 70 includes a material having conductivity. The third electrode 70 is connected to the conductive section 94 using the wiring 71 .

“Storage Element”

FIG. 2 is an enlarged cross-sectional view of the vicinity of the storage element 100 of the semiconductor device according to the first embodiment. FIG. 3 is a plan view of the storage element 100 of the semiconductor device according to the first embodiment. The storage element 100 includes the first ferromagnetic layer 10 , the magnetic recording layer 20 , the nonmagnetic layer 30 , the first electrode 40 , and the second electrode 50 . FIG. 2 is a cross-sectional view of the storage element 100 taken along the xz plane (plane A-A in FIG. 3 ) passing through the center of the magnetic recording layer in the y direction. In FIG. 2 , the insulating layer 80 around the magnetic recording layer 20 , the nonmagnetic layer 30 , and the first ferromagnetic layer 10 are omitted for simplicity.

“First Electrode and Second Electrode”

The first electrode 40 and the second electrode 50 are located on an opposite side of the nonmagnetic layer 30 with respect to the magnetic recording layer 20 . The first electrode 40 and the second electrode 50 are located inside the insulating layer 80 . The first electrode 40 is located between the magnetic recording layer 20 and the conductive section 96 and the second electrode 50 is located between the magnetic recording layer 20 and the conductive section 92 . At least a part of the first electrode 40 and the magnetic recording layer 20 overlap in the z direction. At least a part of the second electrode 50 and the magnetic recording layer 20 overlap in the z direction.

Shapes of the first electrode 40 and the second electrode 50 when viewed in a plan view from the z direction are not particularly limited. For example, the first electrode 40 and the second electrode 50 illustrated in FIG. 3 are rectangular when viewed in a plan view from the z direction.

The first electrode 40 includes a magnetic material. The first electrode 40 has, for example, a magnetization M 40 oriented in one direction. A direction of the magnetization M 40 of the first electrode 40 is different from a direction of a magnetization M 10 of the first ferromagnetic layer 10 . The magnetization M 40 illustrated in FIG. 2 is oriented, for example, in a −z direction. A coercivity of the first electrode 40 is larger than a coercivity of a third region R 3 of the magnetic recording layer 20 which will be described later. The coercivity of the third region R 3 is substantially equal to a coercivity of the magnetic recording layer 20 when the magnetic recording layer 20 is formed above the insulating layer 80 in which the first electrode 40 and the second electrode 50 are not provided.

A difference in coercivity between the first electrode 40 and the third region R 3 can be adjusted according to selection of a material constituting the first electrode 40 and a material constituting the magnetic recording layer 20 . Furthermore, the first electrode 40 may be formed to have a synthetic antiferromagnetic structure (an SAF structure). The synthetic antiferromagnetic structure is composed of two magnetic layers having a nonmagnetic layer disposed therebetween. Magnetizations of the two magnetic layers are fixed and directions of the fixed magnetizations are opposite. For example, a nonmagnetic layer and a ferromagnetic layer are provided below the first electrode 40 illustrated in FIG. 1 . When the first electrode 40 is coupled to the ferromagnetic layer, coercivity of the first electrode 40 increases.

The first electrode 40 is made of, for example, a metal selected from the group consisting of Cr, Mn, Co, Fe, and Ni, alloys containing at least one of these metals, alloys containing at least one metal of these metals and at least one element from B, C, and N, and the like. The first electrode 40 is made of, for example, Co—Fe, Co—Fe—B, Ni—Fe, or the like.

The second electrode 50 is a conductor. The second electrode is made of, for example, Al, Cu, Ag, or the like having excellent conductivity.

“Magnetic Recording Layer”

The magnetic recording layer 20 is located in the z direction from the first electrode 40 and the second electrode 50 . The magnetic recording layer 20 is formed over first surfaces 40 a and 50 a . The magnetic recording layer 20 may be directly connected to the first surfaces 40 a and 50 a and may be connected to the first surfaces 40 and 50 a via a layer therebetween.

The magnetic recording layer 20 is a layer on which information can be recorded using a change in internal magnetic state. The magnetic recording layer 20 is a magnetic layer located closer to the first electrode 40 and the second electrode 50 side than the nonmagnetic layer 30 . The magnetic recording layer 20 extends in the x direction. The magnetic recording layer 20 illustrated in FIG. 2 has a rectangular shape in which the x direction of the magnetic recording layer 20 is a long axis and the y direction thereof is a short axis when viewed in a plan view from the z direction.

The magnetic recording layer 20 has a first magnetic domain 28 and a second magnetic domain 29 therein. A magnetization M 28 of the first magnetic domain 28 and a magnetization M 29 of the second magnetic domain 29 are oriented in opposite directions. A boundary between the first magnetic domain 28 and the second magnetic domain 29 is a magnetic domain wall 27 . The magnetic recording layer 20 can have the magnetic domain wall 27 therein. In the storage element 100 illustrated in FIG. 2 , the magnetization M 28 of the first magnetic domain 28 is oriented in a +z direction and the magnetization M 29 of the second magnetic domain 29 is oriented in the −z direction. Although a description will be provided using an example in which a magnetization is oriented in a z-axis direction below, magnetizations of the magnetic recording layer 20 and the first ferromagnetic layer 10 may be oriented in an x-axis direction and may be oriented in any direction in the xy plane.

The storage element 100 records data in a multi-valued manner or continuously in accordance with a position of the magnetic domain wall 27 of the magnetic recording layer 20 . The data recorded on the magnetic recording layer 20 is read out as a change in resistance value of the storage element 100 when a read current is applied.

A ratio between the first magnetic domain 28 and the second magnetic domain 29 in the magnetic recording layer 20 changes if the magnetic domain wall 27 moves. The magnetization M 10 of the first ferromagnetic layer 10 is in the same direction (parallel) as the magnetization M 28 of the first magnetic domain 28 and is in an opposite direction (anti-parallel) to the magnetization M 29 of the second magnetic domain 29 . If the magnetic domain wall 27 moves in a +x direction and an area of the first magnetic domain 28 in a portion in which the magnetic domain wall 27 and the first ferromagnetic layer 10 overlap when viewed in a plan view from the z direction increases, a resistance value of the storage element 100 decreases. On the other hand, if the magnetic domain wall 27 moves in a −x direction and an area of the second magnetic domain 29 in a portion in which the magnetic domain wall 27 and the first ferromagnetic layer 10 overlap when viewed in a plan view from the z direction increases, a resistance value of the storage element 100 increases.

The magnetic domain wall 27 moves when a write current flows through the magnetic recording layer 20 in the x direction thereof or an external magnetic field is applied to the magnetic recording layer 20 . For example, if a write current (for example, a current pulse) is applied to the magnetic recording layer 20 in the +x direction thereof, the magnetic domain wall 27 moves. At this time, electrons flow in the −x direction opposite to that of a current. When a current flows from the first magnetic domain 28 toward the second magnetic domain 29 , electrons spin-polarized in the second magnetic domain 29 reverse the magnetization M 28 of the first magnetic domain 28 . The magnetic domain wall 27 moves when the magnetization M 28 of the first magnetic domain 28 reverses.

The magnetic recording layer 20 can be divided into a plurality of different regions. Hereinafter, the plurality of regions are referred to as a first region R 1 , a second region R 2 , and a third region R 3 for convenience. A part of the magnetic recording layer 20 overlaps with the first electrode 40 and the second electrode 50 when viewed in a plan view from the z direction.

A region in which the magnetic recording layer 20 , the first electrode 40 , and the first ferromagnetic layer 10 overlap when viewed from the z direction is referred to as the first region R 1 . The first region R 1 is, for example, a region of the magnetic recording layer 20 in which the magnetic recording layer 20 , an upper surface of the first electrode 40 , and a lower surface of the first ferromagnetic layer 10 overlap and is, for example, a region in which the first ferromagnetic layer 10 , the magnetic recording layer 20 , and the first electrode 40 overlap in the z direction among a region in which the magnetic recording layer 20 is in contact with the first electrode 40 .

A region in which the magnetic recording layer 20 , the second electrode 50 , and the first ferromagnetic layer 10 overlap when viewed from the z direction is referred to as the second region R 2 . The second region R 2 is, for example, a region of the magnetic recording layer 20 in which the magnetic recording layer 20 , an upper surface of the second electrode 50 , and the lower surface of the first ferromagnetic layer 10 overlap and is, for example, a region in which the first ferromagnetic layer 10 , the magnetic recording layer 20 , and the second electrode 50 overlap in the z direction among a region in which the magnetic recording layer 20 is in contact with the second electrode 50 .

A region present between the first region R 1 and the second region R 2 is referred to as the third region R 3 . The third region R 3 is, for example, a region of the magnetic recording layer 20 in which the first region R 1 and the second region R 2 are excluded.

A magnetization direction of the first region R 1 is fixed by the magnetization M 40 of the first electrode 40 . The magnetization of the second region R 2 is not fixed. However, since the second region R 2 is in contact with the second electrode 50 , a current density of the second region R 2 is smaller than a current density of the third region R 3 and an amount of change of a current density when a current reaches the second region R 2 from the third region R 3 is larger than an amount of change of a current density of a current flowing in the third region. For this reason, the magnetic domain wall 27 does not easily enter the second region R 2 from the third region R 3 and a movement range of the magnetic domain wall 27 is limited.

The first region R 1 has a first section R 1 a . The first section R 1 a is a surface in the first region R 1 in which the magnetic recording layer 20 faces the first electrode 40 . The first section R 1 a is, for example, a surface in the first region R 1 in which the magnetic recording layer 20 is in contact with the first electrode 40 . The second region R 2 has a second section R 2 a . The second section R 2 a is a surface in the second region R 2 in which the magnetic recording layer 20 faces the second electrode 50 . The second section R 2 a is, for example, a surface in the second region R 2 in which the magnetic recording layer 20 is in contact with the second electrode 50 . An area of the first section R 1 a is larger than an area of the second section R 2 a . In the example illustrated in FIG. 3 , widths w y of the first section R 1 a and the second section R 2 a in they direction are the same and a width w x1 of the first section R 1 a in the x direction is wider than a width w x2 of the second section R 2 a in the x direction.

The magnetic recording layer 20 is made of a magnetic material. The magnetic material constituting the magnetic recording layer 20 can be a metal selected from the group consisting of Cr, Mn, Co, Fe, and Ni, alloys containing at least one of these metals, alloys containing at least one metal of these metals and at least one element from B, C, and N, or the like. To be specific, Co—Fe, Co—Fe—B, and Ni—Fe may be exemplified.

It is desirable that the magnetic recording layer 20 include at least one element selected from the group consisting of Co, Ni, Pt, Pd, Gd, Tb, Mn, Ge, and Ga. Examples of the material used for the magnetic recording layer 20 include a laminated film made of Co and Ni, a laminated film made of Co and Pt, a laminated film made of Co and Pd, a MnGa-based material, a GdCo-based material, and a TbCo-based material. Ferrimagnetic materials such as a MnGa-based material, a GdCo-based material, and a TbCo-based material have a small saturation magnetization and a small threshold value current for moving a magnetic domain wall. Furthermore, a laminated film made of Co and Ni, a laminated film made of Co and Pt, and a laminated film made of Co and Pd have a large coercivity and a slow moving speed of a magnetic domain wall.

“Nonmagnetic Layer”

The nonmagnetic layer 30 is located between the first ferromagnetic layer 10 and the magnetic recording layer 20 . The nonmagnetic layer 30 is laminated on a second surface 20 b of the magnetic recording layer 20 . The second surface 20 b is a surface opposite to the first surfaces 20 a.

The nonmagnetic layer 30 is made of, for example, a nonmagnetic insulator, a semiconductor, or a metal. Examples of the nonmagnetic insulator include Al 2 O 3 , SiO 2 , MgO, MgAl 2 O 4 , and materials in which Al, Si, and Mg are partially substituted with Zn, Be, or the like. These materials have a large band gap and excellent insulating properties. When the nonmagnetic layer 30 is formed of a nonmagnetic insulator, the nonmagnetic layer 30 is a tunnel barrier layer. Examples of nonmagnetic metals include Cu, Au, Ag, and the like. Furthermore, examples of a nonmagnetic semiconductor include Si, Ge, CuInSe 2 , CuGaSe 2 , Cu(In, Ga)Se 2 , and the like.

A thickness of the nonmagnetic layer 30 is preferably 20 Å or more and more preferably 30 Å or more. If the thickness of the nonmagnetic layer 30 is large, a resistance area product (RA) of a recording element 100 increases. The resistance area product (RA) of the recording element 100 is preferably 1×10 5 Ωμm 2 or more and more preferably 1×10 6 Ωμm 2 or more. The resistance area product (RA) of the recording element 100 is represented by a product of an element resistance of one recording element 100 and an element cross-sectional area of the recording element 100 (an area of a virtual cross-section obtained by cutting the nonmagnetic layer 30 along the xy plane).

“First Ferromagnetic Layer”

The first ferromagnetic layer 10 is located in a +z direction of the nonmagnetic layer 30 . The first ferromagnetic layer 10 faces the nonmagnetic layer 30 . The first ferromagnetic layer 10 has a portion in which the first ferromagnetic layer 10 overlaps with a part of the first electrode 40 and a part of the second electrode 50 when viewed from the z direction. The first ferromagnetic layer 10 partially overlaps with the first region R 1 and the second region R 2 when viewed from the z direction.

The first ferromagnetic layer 10 is a magnetization fixed layer having a magnetization M 10 oriented in one direction. A direction in which the magnetization M 10 is oriented is opposite to a direction in which the magnetization M 40 of the first electrode 40 is oriented. A magnetization direction of the magnetization fixed layer is less likely to change than that of the magnetic recording layer 20 when a predetermined external force is applied to the magnetization fixed layer. A predetermined external force is, for example, an external force applied to magnetization using an external magnetic field or an external force applied magnetization using a spin-polarized current.

The first ferromagnetic layer 10 includes a ferromagnetic material. Examples of a ferromagnetic material constituting the first ferromagnetic layer 10 include a metal selected from the group consisting of Cr, Mn, Co, Fe, and Ni, an alloy containing at least one metal of these metals, an alloy containing at least one metal of these metals and at least one element of B, C, and N, and the like. To be specific, Co—Fe, Co—Fe—B, and Ni—Fe are exemplified.

A material constituting the first ferromagnetic layer 10 may be a Heusler alloy. The Heusler alloy is a half-metal and has a high spin polarization. The Heusler alloy is an intermetallic compound having a chemical composition of XYZ or X 2 YZ. X represents a Co-, Fe-, Ni-, or Cu-group transition metal element or a noble metal element in the periodic table, Y represents a Mn-, V-, Cr-, or Ti-group transition metal or an element of the X type in the periodic table, and Z represents a typical element from Group III to Group V. Examples of the Heusler alloy include Co 2 FeSi, Co 2 FeGe, Co 2 FeGa, Co 2 MnSi, Co 2 Mn 1-a Fe a Al b Si 1-b , Co 2 FeGe 1-c Ga c , and the like.

A film thickness of the first ferromagnetic layer 10 is preferably 1.5 nm or less and more preferably 1.0 nm or less when an easy magnetization axis of the first ferromagnetic layer 10 is assumed to a z direction (a perpendicular magnetization film is assumed). If the film thickness of the first ferromagnetic layer 10 is reduced, perpendicular magnetic anisotropy (interface perpendicular magnetic anisotropy) can be added to the first ferromagnetic layer 10 at an interface between the first ferromagnetic layer 10 and another layer (the nonmagnetic layer 30 ). Magnetization of the first ferromagnetic layer 10 is easily oriented in the z direction.

The magnetization of the first ferromagnetic layer 10 is fixed, for example, in the z direction. When the magnetization is fixed in the z direction, it is desirable that the first ferromagnetic layer 10 be a laminate of a ferromagnetic material selected from the group consisting of Co, Fe, and Ni and a nonmagnetic material selected from the group consisting of Pt, Pd, Ru, and Rh and it is more desirable to insert a nonmagnetic material selected from the group consisting of Ir and Ru as an intermediate layer at any position in the laminate. If a ferromagnetic material and a nonmagnetic material are laminated, it is possible to add perpendicular magnetic anisotropy and when the intermediate layer is inserted, it is possible to more strongly fix the magnetization of the first ferromagnetic layer 10 in a perpendicular direction.

The first ferromagnetic layer 10 may have an SAF structure. An antiferromagnetic layer may be provided on a surface of the first ferromagnetic layer 10 opposite to the nonmagnetic layer 30 via a spacer layer. If the first ferromagnetic layer 10 and an antiferromagnetic layer are antiferromagnetically coupled, coercivity of the first ferromagnetic layer 10 increases. The antiferromagnetic layer is, for example, IrMn, PtMn, or the like. The spacer layer includes, for example, at least one selected from the group consisting of Ru, Ir, and Rh.

The semiconductor device according to the first embodiment is obtained by laminating each layer and processing each of the layers to have a predetermined shape. Each of the layers can be laminated using a sputtering method, a chemical vapor deposition (CVD) method, an electron beam evaporation method (EB evaporation method), an atomic laser deposition method, or the like. Each of the layers can be processed using photolithography or the like.

In the storage element 100 according to the first embodiment, if the area of the first section R 1 a in the first region R 1 is larger than the area of the second section R 2 a in the second region R 2 , a range (a dynamic range) of resistance change of the storage element 100 widens.

A resistance value of the storage element 100 changes on the basis of a difference between relative angles of magnetizations of two ferromagnetic materials (the first ferromagnetic layer 10 and the magnetic recording layer 20 ) having the nonmagnetic layer 30 disposed therebetween. The first ferromagnetic layer 10 reaches the first region R 1 and the second region R 2 when viewed in a plan view from the z direction. Therefore, the resistance value of the storage element 100 is determined using magnetization directions of the first region R 1 , the second region R 2 , and the third region R 3 . On the other hand, as described above, the magnetic domain wall 27 does not easily enter the first region R 1 and the second region R 2 . That is to say, although the first region R 1 and the second region R 2 in which the directions of the magnetization thereof are fixed have a large influence on a reference resistance of data of “0” and “1” in the storage element 100 , an influence on the resistance change of the storage element 100 is smaller than that of the third region R 3 .

In the storage element 100 , a resistance value decreases when the magnetic domain wall 27 approaches the first region R 1 and the resistance value increases when the magnetic domain wall 27 approaches the second region R 2 . If an area occupied by the first region R 1 in the magnetic recording layer 20 increases, a minimum resistance value of the storage element 100 increases. Furthermore, if an area occupied by the second region R 2 in the magnetic recording layer 20 increases, a maximum resistance value of the storage element 100 decreases. The storage element 100 can have a larger range of change in resistance when a minimum resistance value increases compared with when a maximum resistance value decreases.

A specific example will be illustrated and described below. First, as assumption conditions, when there is no domain wall 27 and the magnetization M 10 of the first ferromagnetic layer 10 and the magnetization M 28 of the magnetic recording layer 20 are fully parallel in the entire region, a resistance value indicated by the storage element 100 is assumed to be 100Ω. In addition, when there is no magnetic domain wall 27 and the magnetization M 10 of the first ferromagnetic layer 10 and the magnetization M 29 of the magnetic recording layer 20 are fully antiparallel in the entire region, a resistance value indicated by the storage element 100 is assumed to be 200Ω. In this case, the storage element 100 has a maximum range of change in resistance of 100Ω. On the other hand, when the first region R 1 and the second region R 2 are present, a movement range of the magnetic domain wall 27 is limited to the third region R 3 . Thus, the magnetization M 10 of the first ferromagnetic layer 10 and the magnetizations M 28 and M 29 of the magnetic recording layer 20 cannot be fully parallel or fully antiparallel. That is to say, a range of change in resistance of the storage element 100 is less than 100Ω.

First, as Comparative Example 1, a range of change in resistance of a storage element 100 when a first region R 1 and a second region R 2 each occupy regions corresponding to 10% of a magnetic recording layer 20 is obtained. The storage element 100 indicates a minimum resistance value when a magnetic domain wall 27 is located at a boundary between the first region R 1 and a third region R 3 and indicates a maximum resistance value when the magnetic domain wall 27 is located at a boundary between the second region R 2 and the third region R 3 . When the storage element 100 indicates the minimum resistance value, a magnetization M 28 corresponding to 90% of the magnetic recording layer 20 is parallel to a magnetization M 10 of a first ferromagnetic layer 10 and a magnetization M 29 corresponding to 10% of the magnetic recording layer 20 is antiparallel to a magnetization M 10 of the first ferromagnetic layer 10 . The minimum resistance value indicated by the storage element 100 is 105.3Ω. On the other hand, when the storage element 100 indicates the maximum resistance value, the magnetization M 28 corresponding to 10% of the magnetic recording layer 20 is parallel to the magnetization M 10 of the first ferromagnetic layer 10 and the magnetization M 29 corresponding to 90% of the magnetic recording layer 20 is antiparallel to the magnetization M 10 of the first ferromagnetic layer 10 . The maximum resistance value indicated by the storage element 100 is 181.8Ω. A range of change in resistance of the storage element 100 is 76.6Ω and an MR ratio of the storage element 100 is 72.7.

Next, as Comparative Example 2, a range of change in resistance of a storage element 100 when a first region R 1 occupies a region corresponding to 5% of a magnetic recording layer 20 and a second region R 2 occupies a region corresponding to 15% of the magnetic recording layer 20 is obtained. When the storage element 100 indicates a minimum resistance value, a magnetization M 28 corresponding to 95% of the magnetic recording layer 20 is parallel to a magnetization M 10 of the first ferromagnetic layer 10 and the magnetization M 29 corresponding to 5% of the magnetic recording layer 20 is antiparallel to the magnetization M 10 of the first ferromagnetic layer 10 . The minimum resistance value indicated by the storage element 100 is 102.6Ω. On the other hand, when the storage element 100 indicates the maximum resistance value, a magnetization M 28 corresponding to 15% of the magnetic recording layer 20 is parallel to the magnetization M 10 of the first ferromagnetic layer 10 and a magnetization M 29 corresponding to 85% of the magnetic recording layer 20 is antiparallel to the magnetization M 10 of the first ferromagnetic layer 10 . The maximum resistance value indicated by the storage element 100 is 173.9Ω. A range of change in resistance of the storage element 100 is 71.3Ω and an MR ratio of the storage element 100 is 69.6.

Finally, as Example 1, a range of change in resistance of a storage element 100 when a first region R 1 occupies a region corresponding to 15% of a magnetic recording layer 20 and a second region R 2 occupies a region corresponding to 5% of the magnetic recording layer 20 is obtained. When the storage element 100 indicates a minimum resistance value, a magnetization M 28 corresponding to 85% of the magnetic recording layer 20 is parallel to a magnetization M 10 of a first ferromagnetic layer 10 and a magnetization M 29 corresponding to 15% of the magnetic recording layer 20 is antiparallel to the magnetization M 10 of the first ferromagnetic layer 10 . The minimum resistance value indicated by the storage element 100 is 105.3Ω. On the other hand, when the storage element 100 indicates a maximum resistance value, a magnetization M 28 corresponding to 5% of the magnetic recording layer 20 is parallel to the magnetization M 10 of the first ferromagnetic layer 10 and a magnetization M 29 corresponding to 95% of the magnetic recording layer 20 is antiparallel to the magnetization M 10 of the first ferromagnetic layer 10 . The maximum resistance value indicated by the storage element 100 is 190.5Ω. A range of change in resistance of the storage element 100 is 82.4Ω and an MR ratio of the storage element 100 is 76.2.

As illustrated in Example 1, Comparative Example 1, and Comparative Example 2, if proportions in the magnetic recording layer 20 occupied by the first region R 1 and proportions in the magnetic recording layer 20 occupied by the second region R 2 are changed, the ranges of change in resistance of the MR ratios of the storage element 100 change. In Example 1, the proportion in the magnetic recording layer 20 occupied by the first region R 1 is larger than the proportion in the magnetic recording layer 20 occupied by the second region R 2 . Thus, the range of change in resistance and the MR ratio of the storage element 100 are larger than those in Comparative Example 1 and Comparative Example 2. This relationship is not limited to these examples and is not limited also when percentages occupied by the first region R 1 and the second region R 2 are changed and if a value of a resistance value set as an assumption condition is changed on the assumption that the proportion in the magnetic recording layer 20 occupied by the first region R 1 is larger than the proportion in the magnetic recording layer 20 occupied by the second region R 2 .

That is to say, in the storage element 100 according to the first embodiment, an area of the first section R 1 a in the first region R 1 is larger than an area of the second section R 2 a in the second region R 2 . Thus, a range (a dynamic range) of a resistance change of the storage element 100 is wide.

The storage element 100 can record data not in a digital signal of “1” and “0” but in an analog manner. For this reason, the semiconductor device 200 functions as a neuromorphic device configured to imitate the brain.

Magnetization directions of the first ferromagnetic layer 10 , the magnetic recording layer 20 , and the first electrode 40 in the storage element 100 can be confirmed by, for example, measuring a magnetization curve. The magnetization curve can be measured, for example, using a magneto optical Kerr effect (MOKE). The measurement using the MOKE is a measurement method in which linearly polarized light is incident on an object to be measured and which is performed using a magnetooptical effect (a magnetic Kerr effect) in which rotation or the like of a polarization direction occurs.

For example, a case in which an orientation direction of the magnetization of each of the first region R 1 , the second region R 2 , and the third region R 3 in the magnetic recording layer 20 is measured will be described in detail as an example. First, the storage element 100 is ground in the z direction and the first ferromagnetic layer 10 is removed. Since the nonmagnetic layer 30 has a large influence on the orientation direction of the magnetization of the magnetic recording layer 20 , a part of the nonmagnetic layer 30 remains. Subsequently, a magnetic field sufficient to orient the magnetizations M 28 and M 29 of the magnetic recording layer 20 in one direction is applied in a predetermined direction. Moreover, the magnetization curve is measured while an applied magnetic field gradually decreases. A place to be measured is a central position on the xy plane of each of the first region R 1 , the second region R 2 , and the third region R 3 . In the measured magnetization curve, it is possible to identify a magnetization direction due to the positive and negative of magnetization when the applied magnetic field is zero for the first time. It is possible to also measure magnetization directions of the first ferromagnetic layer 10 and the first electrode 40 in the same manner.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to specific embodiments and various modifications and changes are possible without departing from the gist of the present invention described in the claims.

(First Modification)

FIG. 4 is a schematic plan view of a first modification of the semiconductor device according to the first embodiment. A storage element 100 A illustrated in FIG. 4 and the storage element 100 illustrated in FIG. 3 differ in that shapes of a first electrode 41 and a second electrode 51 when viewed in a plan view from the z direction have circular shapes. Other constitutions illustrated in FIG. 4 are the same as those of the storage element 100 illustrated in FIG. 3 , constituent elements in FIG. 4 that are the same as those of FIG. 3 will be denoted with the same reference numerals as in FIG. 3 , and a description thereof will be omitted.

A magnetic recording layer 20 overlaps with a first electrode 41 and a second electrode 51 when viewed in a plan view from the z direction. An area of a first section R 1 a illustrated in FIG. 4 is larger than an area of a second section R 2 a . In the example illustrated in FIG. 4 , a maximum width w x1 in the x direction of a portion in which the first section R 1 a and the magnetic recording layer 20 overlap is larger than a maximum width w x2 in the x direction of a portion in which the second section R 2 a and the magnetic recording layer 20 overlap. Also in the storage element 100 A according to the first modification, an area of a first section R 1 a in a first region R 1 is larger than an area of a second section R 2 a in a second region R 2 . Thus, a range (a dynamic range) of a resistance change of the storage element 100 A is wide. Furthermore, shapes of the first electrode 41 and the second electrode 51 when viewed in a plan view from the z direction are not limited to the rectangular shape illustrated in FIG. 3 and the circular shape illustrated in FIG. 4 and it is possible to select various shapes.

(Second Modification)

FIG. 5 is a schematic cross-sectional view of a second modification of the semiconductor device according to the first embodiment. A storage element 100 B illustrated in FIG. 5 and the storage element 100 illustrated in FIG. 2 differ in that a second electrode 52 in the storage element 100 B illustrated in FIG. 5 is made of a magnetic material. Other constitutions illustrated in FIG. 5 are the same as those of the storage element 100 illustrated in FIG. 1 , constituent elements in FIG. 5 that are the same as those of FIG. 1 will be denoted with the same reference numerals as in FIG. 1 , and a description thereof will be omitted.

A second electrode 52 includes a magnetic material. The second electrode 52 has, for example, a magnetization M 52 oriented in one direction. A direction of the magnetization M 52 of the second electrode 52 is the same as a direction of a magnetization M 10 of a first ferromagnetic layer 10 and is opposite to a direction of a magnetization M 40 of a first electrode 40 . The magnetization M 52 illustrated in FIG. 5 is oriented in the +z direction. Coercivity of the second electrode 52 is larger than coercivity of a third region R 3 of a magnetic recording layer 20 .

For the second electrode 52 , the same constitution and material as in the first electrode 40 can be used. For example, the second electrode may have a synthetic antiferromagnetic structure.

Also in the storage element 100 B according to the second modification, an area of a first section R 1 a in a first region R 1 is larger than an area of a second section R 2 a in a second region R 2 . Thus, a range (a dynamic range) of a resistance change of the semiconductor device 100 B is wide. The magnetization M 52 of the second electrode 52 fixes a magnetization of the second region R 2 in the magnetic recording layer 20 . When the magnetization of the second region R 2 is fixed, it is possible to further prevent the magnetic domain wall 27 from entering the second region R 2 .

(Third Modification)

FIG. 6 is a schematic cross-sectional view of a third modification of the storage element of the semiconductor device according to the first embodiment. FIG. 7 is a schematic plan view of the third modification of the storage element of the semiconductor device according to the first embodiment. FIG. 6 is the cross-sectional view of the storage element cut along an xz plane in a plane A-A in FIG. 7 . A storage element 100 C and the storage element 100 illustrated in FIG. 1 differ in that a shape of a lateral surface of a storage element in the x direction in the storage element 100 C is different. Other constitutions illustrated in FIG. 6 are the same as those of the storage element 100 illustrated in FIG. 1 , constituent elements in FIG. 6 that are the same as those of FIG. 1 will be denoted with the same reference numerals as in FIG. 1 , and a description thereof will be omitted.

A first ferromagnetic layer 11 has a magnetization M 11 and has a first lateral surface 11 S 1 and a second lateral surface 11 S 2 in the x direction. A nonmagnetic layer 31 has a first lateral surface 31 S 1 and a second lateral surface 31 S 2 in the x direction. A magnetic recording layer 21 has a first lateral surface 2151 and a second lateral surface 21 S 2 in the x direction. The first lateral surfaces 11 S 1 , 31 S 1 , and 21 S 1 are lateral surfaces closer to a first electrode 43 among two lateral surfaces in the x direction of each of the first ferromagnetic layer 11 , the nonmagnetic layer 31 , and the magnetic recording layer 21 . The second lateral surfaces 1152 , 31 S 2 , and 21 S 2 are lateral surfaces closer to a second electrode 53 among two lateral surfaces in the x direction of each of the first ferromagnetic layer 11 , the nonmagnetic layer 31 , and the magnetic recording layer 21 . The first lateral surfaces 11 S 1 , 31 S 1 , and 21 S 1 and the second lateral surfaces 11 S 2 , 31 S 2 , and 21 S 2 are inclined with respect to the z direction. A tangent of the first lateral surfaces 11 S 1 , 31 S 1 , and 21 S 1 has, for example, an inclination angle θ 1 with respect to the z direction. A tangent of the second lateral surfaces 11 S 2 , 31 S 2 , and 21 S 2 has, for example, an inclination angle θ 2 with respect to the z direction. Furthermore, the inclination angles θ 1 and 02 may be constant regardless of positions of tangential contacts at which tangents are drawn or may change in accordance with positions of tangential contacts at which tangents are drawn. The inclination angles θ 1 and 02 illustrated in FIG. 6 change in accordance with positions at which tangents are drawn.

The first electrode 43 has a magnetization M 43 . The first electrode 43 has a first lateral surface 43 S 1 and a second lateral surface 43 S 2 in the x direction on a virtual cross-section passing through a center of the magnetic recording layer 20 in the y direction and cut along an xz plane. The second lateral surface 43 S 2 is located closer to the second electrode 53 than the first lateral surface 43 S 1 . The first lateral surface 43 S 1 has a first inclined section 43 p 1 and a second section 43 p 2 . The first inclined section 43 p 1 is inclined with respect to the z direction. A tangent of the first inclined section 43 p 1 has, for example, an inclination angle φ 1 with respect to the z direction. The first inclined section 43 p 1 has an inclination angle with respect to the z direction larger than that of the second lateral surface 43 S 2 . The first lateral surface 43 S 1 changes discontinuously at a boundary between the first inclined section 43 p 1 and the second section 43 p 2 .

The first lateral surfaces 11 S 1 , 31 S 1 , and 21 S 1 and the first inclined section 43 p 1 are continuous. For example, in the xz plane, when asymptotes of the first lateral surfaces 11 S 1 , 31 S 1 , and 21 S 1 and the first inclined section 43 p 1 are drawn using a continuous straight line or curved line, the first lateral surfaces 11 S 1 , 31 S 1 , and 21 S 1 and the first inclined section 43 p 1 can be regarded as continuously changing.

The second electrode 53 has a first lateral surface 53 S 1 and a second lateral surface 53 S 2 in the x direction on a virtual cross-section passing through a center of the magnetic recording layer 20 in the y direction and cut along the xz plane. The second lateral surface 53 S 2 is located closer to the first electrode 43 than the first lateral surface 53 S 1 . The first lateral surface 53 S 1 has a first inclined section 53 p 1 and a second section 53 p 2 . The first inclined section 53 p 1 is inclined with respect to the z direction. A tangent of the first inclined section 53 p 1 has, for example, an inclination angle φ 2 with respect to the z direction. The first inclined section 53 p 1 has an inclination angle with respect to the z direction larger than that of the second lateral surface 53 S 2 . The first lateral surface 53 S 1 changes discontinuously at a boundary between the first inclined section 53 p 1 and the second section 53 p 2 . The second lateral surfaces 11 S 2 , 31 S 2 , 21 S 2 and the first inclined sections 53 p 1 are continuous.

The first lateral surfaces 11 S 1 , 31 S 1 , 21 S 1 , the second lateral surfaces 11 S 2 , 31 S 2 , and 21 S 2 , and the first inclined sections 43 p 1 and 53 p 1 are formed by removing some of end portions thereof in the x direction from a laminate obtained by sequentially laminating the magnetic recording layer 20 , the nonmagnetic layer 30 , and the first ferromagnetic layer 10 . The processing of the end portions is performed using ion milling, photolithography, or the like.

Magnetization generally has a different value in a region having a different state due to a crystal grain, a surface state, a step, etching damage, and the like and has a mutual influence. Portions exposed after the removal of the end portions in the x direction are damaged. Since the damaged portions may serve as pinning sites because surface states or the like thereof change.

Pinning sites are portion whose magnetization does not easily move. The pinning sites whose magnetization does not easily move due to damage have an influence on neighboring regions and has an effect of fixing magnetization more strongly. The first lateral surface 21 S 1 of the magnetic recording layer 20 serves as a pinning site and further fixes magnetization of the first region R 1 . The first inclined section 43 p 1 of the first electrode 43 serves as a pinning site and further fixes the magnetization M 43 of the first electrode 43 . The first lateral surface 21 S 1 of the magnetic recording layer 20 serves as a pinning site and further fixes the magnetization of the first region R 1 . The second lateral surface 21 S 2 of the magnetic recording layer 20 serves as a pinning site and further fixes magnetization of the second region R 2 .

That is to say, the magnetizations of the first electrode 43 , the first region R 1 , and the second region R 2 do not easily reverse as compared with when the first inclined section 43 p 1 , the first lateral surface 21 S, and the second lateral surface 21 S 2 are not provided. When the magnetizations of the first region R 1 and the second region R 2 are fixed more strongly (the magnetizations thereof do not easily reverse), the magnetic domain wall 27 does not easily enter the first region R 1 and the second region R 2 .

Also in the storage element 100 C according to the third modification, an area of a first section R 1 a in a first region R 1 is larger than an area of a second section R 2 a in a second region R 2 . Thus, a range (a dynamic range) of a resistance change of the storage element 100 C is wide.

Although a case in which both lateral surfaces of the storage element 100 C in the x direction are inclined has been described in the third modification, only one of the lateral surfaces may be inclined. Furthermore, the second electrode 53 may include a magnetic material.

(Fourth Modification)

FIG. 8 is a schematic cross-sectional view of a fourth modification of the storage element of the semiconductor device according to the first embodiment. A storage element 100 D illustrated in FIG. 8 and the storage element 100 C according to the third modification illustrated in FIG. 6 differ in that, in the storage element 100 D illustrated in FIG. 8 , first lateral surfaces 11 S 1 , 31 S 1 , and 21 S 1 and a first inclined section 43 p 1 are discontinuous and second lateral surfaces 1152 , 3152 , and 2152 and a first inclined section 53 p 1 are discontinuous. Other constitutions illustrated in FIG. 8 are the same as those of the storage element 100 C according to the third modification illustrated in FIG. 6 , constituent elements in FIG. 8 that are the same as those of FIG. 6 will be denoted with the same reference numerals as in FIG. 6 , and a description thereof will be omitted.

The first lateral surfaces 11 S 1 , 31 S 1 , and 21 S 1 and the first inclined section 43 p 1 may be discontinuous due to different etching rates in some cases. Similarly, the second lateral surfaces 1152 , 31 S 2 , and 21 S 2 and the first inclined section 53 p 1 may be discontinuous in some cases.

Also in the storage element 100 D according to the fourth modification, an area of a first section R 1 a in a first region R 1 is larger than an area of a second section R 2 a in a second region R 2 . Thus, a range (a dynamic range) of a resistance change of the storage element 100 D is wide.

Also, a first lateral surface 21 S 1 and a second lateral surface 21 S 2 in a magnetic recording layer 20 , and a first inclined section 43 p 1 serve as pinning sites. When magnetizations of the first region R 1 and the second region R 2 are fixed more strongly (the magnetizations thereof do not easily reverse), the magnetic domain wall 27 does not easily enter the first region R 1 and the second region R 2 .

Also, although a case in which both lateral surfaces of the storage element 100 D in the x direction are inclined has been described in the fourth modification, only one of the lateral surfaces may be inclined. Furthermore, the second electrode 53 may include a magnetic material.

(Fifth Modification)

FIG. 9 is a schematic cross-sectional view of a fifth modification of the storage element according to the first embodiment. Shapes of a first electrode 44 and a second electrode 54 in a storage element 100 E illustrated in FIG. 9 are different from those of the storage element 100 C according to the third modification described with reference to FIG. 6 . Other constitutions illustrated in FIG. 9 are the same as those of the storage element 100 C according to the third modification illustrated in FIG. 6 , constituent elements in FIG. 9 that are the same as those of FIG. 6 will be denoted with the same reference numerals as in FIG. 6 , and a description thereof will be omitted.

A first electrode 44 has a magnetization M 44 . The first electrode 44 has a first lateral surface 44 S 1 and a second lateral surface 44 S 2 in the x direction on a virtual cross-section passing through a center of a magnetic recording layer 20 in the y direction and cut along the xz plane. The second lateral surface 44 S 2 is located closer to the second electrode 54 than the first lateral surface 44 S 1 . The first lateral surface 44 S 1 has a first inclined section 44 p 1 and a second inclined section 44 p 2 . The first inclined section 44 p 1 and the second inclined section 44 p 2 are inclined with respect to the z direction. A tangent of the first inclined section 44 p 1 has, for example, an inclination angle φ 3 with respect to the z direction. A tangent of the second inclined section 44 p 2 has, for example, an inclination angle φ 4 with respect to the z direction. The first inclined section 44 p 1 has an inclination angle with respect to the z direction larger than that of the second lateral surface 44 S 2 . The first lateral surface 44 S 1 changes discontinuously at a boundary between the first inclined section 44 p 1 and the second inclined section 44 p 2 .

The second electrode 54 has a first lateral surface 54 S 1 and a second lateral surface 54 S 2 in the x direction on a virtual cross-section cut along the xz plane. The second lateral surface 54 S 2 is located closer to the first electrode 44 than the first lateral surface 54 S 1 . The first lateral surface 54 S 1 has a first inclined section 54 p 1 and a second inclined section 54 p 2 . The first inclined section 54 p 1 and the second inclined section 54 p 2 are inclined with respect to the z direction. A tangent of the first inclined section 54 p 1 has, for example, an inclination angle φ 5 with respect to the z direction. A tangent of the second inclined section 54 p 2 has, for example, an inclination angle φ 6 with respect to the z direction. The first inclined section 54 p 1 has an inclination angle with respect to the z direction larger than that of the second lateral surface 54 S 2 . The first lateral surface 54 S 1 changes discontinuously at a boundary between the first inclined section 54 p 1 and the second inclined section 54 p 2 .

Also in the storage element 100 E according to the fifth modification, an area of a first section R 1 a in a first region R 1 is larger than an area of a second section R 2 a in a second region R 2 . Thus, a range (a dynamic range) of a resistance change of the storage element 100 E is wide.

Also, a first lateral surface 21 S 1 and a second lateral surface 21 S 2 in the magnetic recording layer 20 , and a first inclined section 44 p 1 serve as pinning sites. When magnetizations of the first region R 1 and the second region R 2 are fixed more strongly (the magnetizations thereof do not easily reverse), the magnetic domain wall 27 does not easily enter the first region R 1 and the second region R 2 .

Also, although a case in which both lateral surfaces of the storage element 100 E in the x direction are inclined has been described in the fifth modification, only one of the lateral surfaces may be inclined. Furthermore, shapes of the first electrode 44 and the second electrode 54 on a cut xz surface is not limited to trapezoid shapes in which lengths of upper bases of the electrodes in the +z direction are shorter than lengths of lower bases of the electrodes in the −z direction and may be trapezoid shapes in which lengths of upper bases of the electrodes in the +z direction are longer than lengths of lower bases of the electrodes in the −z direction. In addition, the second electrode 54 may include a magnetic material.

Second Embodiment

FIG. 10 is a schematic cross-sectional view of a semiconductor device according to a second embodiment. A semiconductor device 201 illustrated in FIG. 10 and the semiconductor device 200 according to the first embodiment differ in that the semiconductor device 201 illustrated in FIG. 10 has a bottom pin structure in which a first ferromagnetic layer 10 is located closer to a substrate 60 than a magnetic recording layer 20 . Other constitutions illustrated in FIG. 10 are the same as those of the semiconductor device 200 illustrated in FIG. 1 , constituent elements in FIG. 10 that are the same as those of FIG. 1 will be denoted with the same reference numerals as in FIG. 1 , and a description thereof will be omitted.

FIG. 11 is a schematic cross-sectional view of a storage element of the semiconductor device according to the second embodiment. A storage element 101 includes a first ferromagnetic layer 10 , a magnetic recording layer 20 , a nonmagnetic layer 30 , a first electrode 40 , and a second electrode 50 . An insulating layer 81 is provided between the first electrode 40 and the second electrode 50 .

The insulating layer 81 that is the same as the insulating layer 80 in the first embodiment is utilized. The insulating layer 81 is formed on a surface of the magnetic recording layer 20 opposite to a surface on the nonmagnetic layer 30 side. The insulating layer 81 covers a third region R 3 of the magnetic recording layer 20 . The insulating layer 81 functions as a cap layer. The cap layer is a layer configured to increase orientation of the magnetization of the magnetic recording layer 20 and protect the magnetic recording layer 20 . When the cap layer is made of an insulator, a current for driving the magnetic domain wall 27 is prevented from being diverted toward the insulating layer 81 side.

The storage element 101 having a bottom pin structure is prepared through the following procedure. First, a first transistor Tr 1 , a second transistor Tr 2 , a third transistor Tr 3 , a first wiring Cm, a second wiring Wp, and a third wiring Rp are formed above the substrate 60 via the insulating layer 80 . Furthermore, the first ferromagnetic layer 10 , the nonmagnetic layer 30 , and the magnetic recording layer 20 are sequentially laminated on one surface of the insulating layer 80 and each of the layers is processed to have a predetermined shape. In addition, the surroundings of the first ferromagnetic layer 10 , the nonmagnetic layer 30 , and the magnetic recording layer 20 are further covered with the insulating layer 80 . Surfaces of the magnetic recording layer 20 and the insulating layer 80 are planarized and then the first electrode 40 and the second electrode 50 are formed. Moreover, the semiconductor device 201 is obtained by burying an insulating layer 81 between the first electrode 40 and the second electrode 50 .

Also in the storage element 101 according to the second embodiment, an area of a first section R 1 a in a first region R 1 is larger than an area of a second section R 2 a in a second region R 2 . Thus, a range (a dynamic range) of a resistance change of the storage element 101 is wide.

For the storage element 101 according to the second embodiment, it is possible to select the same modification as in the storage element 100 according to the first embodiment.

(Six Modification)

FIG. 12 is a schematic cross-sectional view of a sixth modification of the storage element according to the second embodiment. A storage element 101 B illustrated in FIG. 12 and the storage element 101 according to the second embodiment illustrated in FIG. 11 in view of shapes of a first electrode 45 and a second electrode 55 , shapes of a first section R 1 a ′ and a second section R 2 a ′ in the magnetic recording layer 20 , and a relationship between the first electrode 45 and the second electrode 55 and the insulating layer 81 differs. Other constitutions illustrated in FIG. 12 are the same as those of the storage element 101 according to the second embodiment illustrated in FIG. 11 , constituent elements in FIG. 12 that are the same as those of FIG. 11 will be denoted with the same reference numerals as in FIG. 11 , and a description thereof will be omitted.

A first region R 1 in the magnetic recording layer 20 has the first section R 1 a ′. The first section R 1 a ′ corresponds to a surface of the magnetic recording layer 20 in the first region R 1 facing the first electrode 45 . The first section R 1 a ′ corresponds to, for example, a surface of the magnetic recording layer 20 in the first region R 1 in contact with the first electrode 45 . A second region R 2 in the magnetic recording layer 20 has the second section R 2 a ′. The second section R 2 a ′ corresponds to a surface of the magnetic recording layer 20 in the first region R 2 facing the second electrode 55 . The second section R 2 a ′ corresponds to, for example, a surface of the magnetic recording layer 20 in the second region R 2 in contact with the second electrode 55 . An area of the first section R 1 a ′ is larger than an area of the second section R 2 a ′. The first section R 1 a ′ and the second section R 2 a ′ are inclined in the x direction with respect to the z direction. The first surfaces 20 a , the first section R 1 a ′, and the second section R 2 a ′ which are surfaces of the magnetic recording layer 20 in the z direction are discontinuous. The first section R 1 a ′ and the second section R 2 a ′ are formed by milling a part of the magnetic recording layer 20 when a part of the insulating layer 81 is removed.

Also, the first section R 1 a ′ and the second section R 2 a ′ in the magnetic recording layer 20 serve as pinning sites. When magnetizations of the first region R 1 and the second region R 2 are fixed more strongly (the magnetizations thereof do not easily reverse), the magnetic domain wall 27 does not easily enter the first region R 1 and the second region R 2 .

The first electrode 45 and the second electrode 55 have circular arc convex surfaces 45 a and 55 a on a virtual cross-section passing through a center of the magnetic recording layer 20 in the y direction and cut along the xz plane. Surfaces of the first electrode 45 and the second electrode 55 may be formed in a circular arc shape due to surface tension in some cases.

A surface 81 a of the insulating layer 81 is located further in the −z direction than at least a part of the surfaces 45 a and 55 a of the first electrode 45 and the second electrode 55 . Two lateral surfaces 81 S 1 and 81 S 2 of the insulating layer 81 in the x direction are inclined in the x direction with respect to the z direction. The lateral surfaces 81 S 1 and 81 S 2 are formed through milling.

Also in the storage element 101 B according to the sixth modification, an area of the first section R 1 a ′ in the first region R 1 is larger than an area of the second section R 2 a ′ in the second region R 2 . Thus, a range (a dynamic range) of a resistance change of the storage element 101 B is wide.

Third Embodiment

FIG. 13 is a constitution diagram of a magnetic recording array according to a third embodiment. A magnetic recording array 300 includes storage elements 100 , first wirings Cm 1 to Cmn, second wirings Wp 1 to Wpn, third wirings Rp 1 to Rpn, first switching elements 110 , second switching elements 120 , and third switching elements 130 . The first wiring Cm illustrated in FIG. 1 is one of the first wirings Cm 1 to Cmn illustrated in FIG. 12 . The second wiring Wp illustrated in FIG. 1 is one of the second wirings Wp 1 to Wpn illustrated in FIG. 12 . The third wiring Rp illustrated in FIG. 1 is one of the third wirings Rp 1 to Rpn illustrated in FIG. 12 . One of the first switching elements 110 is, for example, the third transistor Tr 3 illustrated in FIG. 1 . One of the second switching elements 120 is, for example, the first transistor Tr 1 illustrated in FIG. 1 . One of the third switching elements 130 is, for example, the second transistor Tr 2 illustrated in FIG. 1 . Furthermore, these storage elements 100 are not limited to the storage elements 100 illustrated in FIG. 1 and may have a constitution of another modification or another embodiment.

<First Wiring, Second Wiring, and Third Wiring>

The first wirings Cm 1 to Cmn are common wirings. Each of the common wirings is a wiring used both at the time of writing data and at the time of reading data. The first wirings Cm 1 to Cmn are electrically connected to a reference potential. For example, when the first wirings Cm 1 to Cmn are grounded, the reference potential serves as a ground. Furthermore, the first wirings Cm 1 to Cmn are connected to at least one storage element 100 among a plurality of storage elements 100 . The first wirings Cm 1 to Cmn may be provided in each of the plurality of storage elements 100 or may be provided over the plurality of storage elements 100 .

The second wirings Wp 1 to Wpn are write wirings. The second wirings Wp 1 to Wpn are electrically connected to at least two or more storage elements 100 among the plurality of storage elements 100 . The second wirings Wp 1 to Wpn are connected to a power supply at the time of using the magnetic recording array 300 .

The third wirings Rp 1 to Rpn are read wirings. The third wirings Rp 1 to Rpn are electrically connected to at least one or more storage elements 100 among the plurality of storage elements 100 . The third wirings Rp 1 to Rpn are connected to the power supply at the time of using the magnetic recording array 300 .

<First Switching Element, Second Switching Element, and Third Switching Element>

The first switching elements 110 are connected between the storage elements 100 and the first wirings Cm 1 to Cmn. The second switching elements 120 are connected between the storage elements 100 and the second wirings Wp 1 to Wpn. The third switching elements 130 are connected between the storage elements 100 and the third wirings Rp 1 to Rpn.

If the first switching element 110 and the second switching elements 120 are turned on, a write current flows between the first wirings Cm 1 to Cmn and the second wirings Wp 1 to Wpn connected to predetermined storage elements 100 . If the first switching elements 110 and the third switching elements 130 are turned on, a read current flows between the first wirings Cm 1 to Cmn and the third wirings Rp 1 to Rpn connected to predetermined storage elements 100 .

The first switching elements 110 , the second switching elements 120 , and the third switching elements 130 are elements configured to control a flow of a current. For example, as the first switching elements 110 , the second switching elements 120 , and the third switching elements 130 , elements such as transistors and ovonic threshold switches (OTSs) in which a phase change of a crystal layer is used, elements such as a metal-insulator transition (MIT) switch in which a change in band structure is used, elements such as Zener diodes and avalanche diodes in which a breakdown voltage is used, elements in which conductivity changes with a change in atomic position, and the like can be utilized.

One of the second switching elements 120 and one the third switching elements 130 may be shared for the storage elements 100 connected to one of second wiring Wp 1 to Wpn or one of third wiring Rp 1 to Rpn. For example, one second switching element 120 may be provided on an upstream side of any of the second wirings Wpn. Furthermore, for example, one third switching element 130 may be provided on an upstream side of any of the third wirings Rpn. It is possible to select a specific storage element 100 by switching turning-on/-off of a first switching element 110 connected to each of the storage elements 100 .

The magnetic recording array 300 includes the plurality of storage elements 100 integrated therein. A range (a dynamic range) of a resistance change of each of the storage elements 100 is wide. Therefore, an influence of noise on data recorded by each of the storage elements 100 is minimized and reliability of data in the magnetic recording array 300 is further improved.

While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims.

10 , 11 First ferromagnetic layer

20 , 21 Magnetic recording layer

27 Magnetic domain wall

28 First magnetic domain

29 Second magnetic domain

30 , 31 Nonmagnetic layer

40 , 41 , 43 , 44 , 45 First electrode

50 , 51 , 52 , 53 , 54 , 55 Second electrode

60 Substrate

70 Interlayer insulating film

80 Insulating layer

100 , 100 A, 100 B, 100 C, 100 D, 100 E, 101 Semiconductor device

110 First switching element

120 Second switching element

130 Third switching element

200 Magnetic recording array

20 a , 40 a , 50 a , 60 a First surface

20 b Second surface

11 S 1 , 21 S 1 , 31 S 1 , 43 S 1 , 44 S 1 , 53 S 1 , 54 S 1 First lateral surface

11 S 2 , 21 S 2 , 31 S 2 , 43 S 2 , 44 S 2 , 53 S 2 , 54 S 2 Second lateral surface

43 p 1 , 44 p 1 , 53 p 1 , 54 p 1 First inclined section

43 p 2 , 53 p 2 Second section

44 p 2 , 54 p 2 Second inclined section

R 1 First region

R 1 a , R 1 a ′ First section

R 2 a , R 2 a ′ Second section

R 2 Second region

R 3 Third region

M 10 , M 11 , M 28 , M 29 , M 40 , M 43 , M 44 , M 52 Magnetization

Cm 1 to Cmn First wiring

Wp 1 to Wpn Second wiring

Rp 1 to Rpn Third wiring