Imaging device

An imaging device comprising:

• a first circuit including a first transistor and a second transistor;
• and
• a second circuit including a third transistor, a fourth transistor, a fifth transistor, a sixth transistor and a photodiode,
• wherein the first transistor, the third transistor and the fourth transistor are each an n-channel transistor comprising an oxide semiconductor layer as an active layer,
• wherein the second transistor is a p-channel transistor,
• wherein an active region of the second transistor is positioned in a silicon substrate,
• 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 a gate of the first transistor is electrically connected to a gate of the second transistor,
• wherein one of a source and a drain of the third transistor is electrically connected to the photodiode,
• wherein the other of the source and the drain of the third transistor is electrically connected to one of a source and a drain of the fourth transistor,
• wherein the other of the source and the drain of the third transistor is electrically connected to a gate of the fifth transistor,
• wherein one of a source and a drain of the fifth transistor is electrically connected to one of a source and a drain of the sixth transistor,
• wherein the photodiode is positioned in the silicon substrate,
• wherein the first transistor and the second transistor overlap each other with an insulating layer therebetween,
• wherein the photodiode and each of the third to sixth transistors overlap each other with the insulating layer therebetween,
• wherein the second transistor is positioned on a first surface of the silicon substrate, and
• wherein the photodiode has a light-receiving surface that is opposite to the first surface of the silicon substrate.

An imaging device comprising:

• a first circuit including a first transistor and a second transistor;
• and
• a second circuit including a third transistor and a photodiode,
• wherein the first transistor and the third transistor are each an n-channel transistor comprising an oxide semiconductor layer,
• wherein the second transistor is a p-channel transistor comprising an active region in a silicon substrate,
• 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 a gate of the first transistor is electrically connected to a gate of the second transistor,
• wherein the photodiode is positioned in the silicon substrate,
• wherein the third transistor and the photodiode overlap each other with an insulating layer therebetween,
• wherein the second transistor is positioned on a first surface of the silicon substrate, and
• wherein the photodiode has a light-receiving surface that is opposite to the first surface of the silicon substrate.