US Patent 9236408 Oxide semiconductor device including photodiode

A solid-state image sensing element including a transistor with stable electrical characteristics (e.g., significantly low off-state current) is provided. Two different element layers (an element layer including an oxide semiconductor layer and an element layer including a photodiode) are stacked over a semiconductor substrate provided with a driver circuit such as an amplifier circuit, so that the area occupied by a photodiode is secured. A transistor including an oxide semiconductor layer in a channel formation region is used as a transistor electrically connected to the photodiode, which leads to lower power consumption of a semiconductor device.