Disclosed is a semiconductor device capable of functioning as a memory device. The memory device comprises a plurality of memory cells, and each of the memory cells contains a first transistor and a second transistor. The first transistor is provided over a substrate containing a semiconductor material and has a channel formation region in the substrate. The second transistor has an oxide semiconductor layer. The gate electrode of the first transistor and one of the source and drain electrodes of the second transistor are electrically connected to each other. The extremely low off current of the second transistor allows the data stored in the memory cell to be retained for a significantly long time even in the absence of supply of electric power.

A semiconductor device includes a two-dimensional semiconductor layer formed by a two-dimensional semiconductor material having a first formation energy, a two-dimensional metal conductor layer formed by a two-dimensional metal material and covering a surface of the two-dimensional semiconductor layer, and a metal layer covering a surface of the two-dimensional metal conductor layer. The two-dimensional metal material has a second formation energy smaller than the first formation energy. The two-dimensional metal conductor layer is formed by bonding of cations from the metal layer and anions from the two-dimensional semiconductor layer. As such, the contact resistances between the two-dimensional materials and the metals can be effectively reduced, enabling the application of the two-dimensional materials in semiconductor devices such as field-effect transistors.

A semiconductor device includes a two-dimensional semiconductor layer formed by a two-dimensional semiconductor material having a first formation energy, a two-dimensional metal conductor layer formed by a two-dimensional metal material and covering a surface of the two-dimensional semiconductor layer, and a metal layer covering a surface of the two-dimensional metal conductor layer. The two-dimensional metal material has a second formation energy smaller than the first formation energy. The two-dimensional metal conductor layer is formed by bonding of cations from the metal layer and anions from the two-dimensional semiconductor layer. As such, the contact resistances between the two-dimensional materials and the metals can be effectively reduced, enabling the application of the two-dimensional materials in semiconductor devices such as field-effect transistors.

Disclosed is a semiconductor device capable of functioning as a memory device. The memory device comprises a plurality of memory cells, and each of the memory cells contains a first transistor and a second transistor. The first transistor is provided over a substrate containing a semiconductor material and has a channel formation region in the substrate. The second transistor has an oxide semiconductor layer. The gate electrode of the first transistor and one of the source and drain electrodes of the second transistor are electrically connected to each other. The extremely low off current of the second transistor allows the data stored in the memory cell to be retained for a significantly long time even in the absence of supply of electric power.

Disclosed is a semiconductor device capable of functioning as a memory device. The memory device comprises a plurality of memory cells, and each of the memory cells contains a first transistor and a second transistor. The first transistor is provided over a substrate containing a semiconductor material and has a channel formation region in the substrate. The second transistor has an oxide semiconductor layer. The gate electrode of the first transistor and one of the source and drain electrodes of the second transistor are electrically connected to each other. The extremely low off current of the second transistor allows the data stored in the memory cell to be retained for a significantly long time even in the absence of supply of electric power.

Disclosed is a semiconductor device capable of functioning as a memory device. The memory device comprises a plurality of memory cells, and each of the memory cells contains a first transistor and a second transistor. The first transistor is provided over a substrate containing a semiconductor material and has a channel formation region in the substrate. The second transistor has an oxide semiconductor layer. The gate electrode of the first transistor and one of the source and drain electrodes of the second transistor are electrically connected to each other. The extremely low off current of the second transistor allows the data stored in the memory cell to be retained for a significantly long time even in the absence of supply of electric power.

Disclosed is a semiconductor device capable of functioning as a memory device. The memory device comprises a plurality of memory cells, and each of the memory cells contains a first transistor and a second transistor. The first transistor is provided over a substrate containing a semiconductor material and has a channel formation region in the substrate. The second transistor has an oxide semiconductor layer. The gate electrode of the first transistor and one of the source and drain electrodes of the second transistor are electrically connected to each other. The extremely low off current of the second transistor allows the data stored in the memory cell to be retained for a significantly long time even in the absence of supply of electric power.

Disclosed is a semiconductor device capable of functioning as a memory device. The memory device comprises a plurality of memory cells, and each of the memory cells contains a first transistor and a second transistor. The first transistor is provided over a substrate containing a semiconductor material and has a channel formation region in the substrate. The second transistor has an oxide semiconductor layer. The gate electrode of the first transistor and one of the source and drain electrodes of the second transistor are electrically connected to each other. The extremely low off current of the second transistor allows the data stored in the memory cell to be retained for a significantly long time even in the absence of supply of electric power.

Disclosed is a semiconductor device capable of functioning as a memory device. The memory device comprises a plurality of memory cells, and each of the memory cells contains a first transistor and a second transistor. The first transistor is provided over a substrate containing a semiconductor material and has a channel formation region in the substrate. The second transistor has an oxide semiconductor layer. The gate electrode of the first transistor and one of the source and drain electrodes of the second transistor are electrically connected to each other. The extremely low off current of the second transistor allows the data stored in the memory cell to be retained for a significantly long time even in the absence of supply of electric power.

A multilayer composite structure and a method of preparing a multilayer composite structure are provided. The multilayer composite structure comprises a semiconductor handle substrate having a minimum bulk region resistivity of at least about 500 ohm-cm and the front surface of the single crystal semiconductor handle substrate has a surface roughness of at least about 0.1 micrometers as measured according to the root mean square method over a surface area of at least 30 micrometers by 30 micrometers. The composite structure further comprises a charge trapping layer in contact with the front surface, the charge trapping layer comprising poly crystalline silicon, the poly crystalline silicon comprising grains having a plurality of crystal orientations; a dielectric layer in contact with the charge trapping layer; and a single crystal semiconductor device layer in contact with the dielectric layer.