Semiconductor device

A semiconductor device comprising a circuit, the circuit comprising:

• a first transistor comprising a first semiconductor layer and a first gate electrode;
• an insulating layer over the first semiconductor layer;
• and
• a second transistor comprising:
• a back gate electrode;
• a second semiconductor layer over the back gate electrode and the insulating layer;
• and
• a second gate electrode over the second semiconductor layer,
• wherein the circuit is an inversion element,
• wherein the first gate electrode is electrically connected to the second gate electrode,
• wherein one of a source and a drain of the first transistor is electrically connected to one of a source and a drain of the second transistor,
• wherein the back gate electrode is configured to control a threshold voltage of the second transistor,
• wherein the insulating layer is interposed between the second semiconductor layer and the back gate electrode,
• wherein the second semiconductor layer includes an oxide semiconductor layer,
• wherein the back gate electrode is formed from a same layer as the first gate electrode,
• wherein the first semiconductor layer includes a silicon layer,
• wherein the back gate electrode extends beyond side edges of the second semiconductor layer in a channel width direction of the second transistor, and
• wherein the second gate electrode extends beyond the side edges of the second semiconductor layer in the channel width direction of the second transistor.

A semiconductor device comprising a circuit, the circuit comprising:

• a first transistor comprising a first semiconductor layer, a first gate electrode and a first back gate electrode;
• an insulating layer over at least a part of the first transistor;
• and
• a second transistor comprising a second back gate electrode, a second semiconductor layer over the second back gate electrode and a second gate electrode over the second semiconductor layer,
• wherein the second back gate electrode is configured to control a threshold voltage of the second transistor,
• wherein the insulating layer is interposed between the second semiconductor layer and the second back gate electrode,
• wherein the second semiconductor layer includes an oxide semiconductor layer,
• wherein the second back gate electrode is formed from a same layer as the first gate electrode, and
• wherein the first semiconductor layer includes a silicon layer.

A semiconductor device comprising a circuit, the circuit comprising:

• a first transistor comprising a first semiconductor layer and a first gate electrode;
• an insulating layer over the first semiconductor layer;
• and
• a second transistor comprising:
• a back gate electrode;
• a second semiconductor layer over the back gate electrode and the insulating layer;
• and
• a second gate electrode over the second semiconductor layer,
• wherein the circuit is a memory element,
• wherein the first gate electrode is electrically connected to one of a source and a drain of the second transistor,
• wherein the back gate electrode is configured to control a threshold voltage of the second transistor,
• wherein the second semiconductor layer includes an oxide semiconductor layer,
• wherein the first semiconductor layer includes a silicon layer,
• wherein the back gate electrode extends beyond side edges of the second semiconductor layer in a channel width direction of the second transistor, and
• wherein the second gate electrode extends beyond the side edges of the second semiconductor layer in the channel width direction of the second transistor.