Patent ID: 9704899
Date: 2017-07-11
CPC Classifications: H01L

Claim:
1. An imaging device comprising: a first layer; a second layer; and a third layer, wherein the first layer, the second layer, and the third layer overlap with one another, wherein the first layer includes a first transistor and a second transistor, wherein the second layer includes a third transistor and a fourth transistor, wherein each of active layers of the first transistor, the second transistor, the third transistor, and the fourth transistor includes an oxide semiconductor, wherein the third layer includes a photoelectric conversion element, 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 one of the source and the drain of the second transistor is electrically connected to a gate of the third transistor, wherein one of a source and a drain of the third transistor is electrically connected to one of a source and a drain of the fourth transistor, wherein one electrode of the photoelectric conversion element is electrically connected to the other one of the source and the drain of the first transistor, wherein off-state currents of the first transistor and the second transistor are lower than those of the third transistor and the fourth transistor, and wherein field-effect mobilities of the third transistor and the fourth transistor are higher than those of the first transistor and the second transistor.