Resistance change nonvolatile storage device and method of controlling the same

A nonvolatile storage device comprising:na memory including at least one nonvolatile resistance storage element; anda control unit configured to write a high resistance state or a low resistance state to the resistance storage element,wherein the control unit applies a bias to the resistance storage element in a verification operation carried out after writing the high resistance state, or applies a bias to the resistance storage element in a verification operation carried out after writing the low resistance state, these biases being in directions opposite to each other,wherein the control unit applies a reverse bias to the resistance storage element at a time of the verification operation carried out after writing the high resistance state, or applies a forward bias to the resistance storage element at a time of the verification operation carried out after writing the low resistance state,wherein a direction of the reverse bias is the direction in which a voltage pulse is applied at a time of writing the high resistance, andwherein a direction of the reverse bias is the direction in which a voltage pulse is applied at a time of writing the low resistance.

A method of controlling a nonvolatile storage device having a memory including at least one nonvolatile resistance storage element, the method comprising:na writing step of writing a high resistance state or a low resistance state to the resistance storage element; anda verification step of verifying successful writing of the high resistance state or the low resistance state carried out after the writing step,wherein the verification step applies a bias to the resistance storage element in a verification operation carried out after writing the high resistance state, or applies a bias to the resistance storage element in a verification operation carried out after writing the low resistance state, these biases being in directions opposite to each other,wherein, in the verification step, a reverse bias is applied to the resistance storage element at a time of the verification operation carried out after writing the high resistance state, or a forward bias is applied to the resistance storage element at a time of the verification operation carried out after writing the low resistance state,wherein a direction of the reverse bias is the direction in which a voltage pulse is applied at a time of writing the high resistance, andwherein a direction of the reverse bias is the direction in which a voltage pulse is applied at a time of writing the low resistance.