Semiconductor device

A semiconductor device comprising:na first transistor comprising silicon;an aluminum oxide film over the first transistor; anda second transistor over the aluminum oxide film, the second transistor comprising:na conductor over and in contact with the aluminum oxide film; andan oxide semiconductor over the conductor,wherein the oxide semiconductor has a lower hydrogen concentration than the silicon, andwherein the oxide semiconductor overlaps with the conductor.

A semiconductor device comprising:na first transistor comprising silicon;an aluminum oxide film over the first transistor; anda second transistor over the aluminum oxide film, the second transistor comprising:na first conductor over the aluminum oxide film;a first insulator over the first conductor;a first oxide semiconductor over the first insulator;a second oxide semiconductor over the first oxide semiconductor;a second conductor and a third conductor over the second oxide semiconductor;a third oxide semiconductor over the second conductor and the third conductor;a second insulator over the third conductor; anda fourth conductor over the third conductor,wherein each of the first oxide semiconductor, the second oxide semiconductor, and the third oxide semiconductor has a lower hydrogen concentration than the silicon.

A semiconductor device comprising:na first transistor comprising silicon;an aluminum oxide film over the first transistor; anda second transistor over the aluminum oxide film, the second transistor comprising:na first conductor over the aluminum oxide film;a first insulator over the first conductor, the first insulator having a projection portion;a first oxide semiconductor over the first insulator, the first oxide semiconductor in contact with a top surface of the projection portion;a second oxide semiconductor over the first oxide semiconductor;a second conductor and a third conductor over the second oxide semiconductor;a third oxide semiconductor over the second conductor and the third conductor;a second insulator over the third conductor; anda fourth conductor over the third conductor,wherein each of the first oxide semiconductor, the second oxide semiconductor, and the third oxide semiconductor has a lower hydrogen concentration than the silicon, andwherein the third oxide semiconductor is in contact with a side surface of the first oxide semiconductor, a top surface and a side surface of the second oxide semiconductor, and a side surface of the projection portion.