Semiconductor device including an oxide semiconductor layer

摘要

A solid-state image sensor which holds a potential for a long time and includes a thin film transistor with stable electrical characteristics is provided. When the off-state current of a thin film transistor including an oxide semiconductor layer is set to 1×10−13 A or less and the thin film transistor is used as a reset transistor and a transfer transistor of the solid-state image sensor, the potential of the signal charge storage portion is kept constant, so that a dynamic range can be improved. When a silicon semiconductor which can be used for a complementary metal oxide semiconductor is used for a peripheral circuit, a high-speed semiconductor device with low power consumption can be manufactured.

主权项

1. A semiconductor device comprising:
a first transistor comprising a gate electrode over a substrate, wherein a channel formation region of the first transistor comprises crystalline silicon; an interlayer insulating film over the first transistor; a second transistor over the interlayer insulating film, the second transistor comprising:
a first oxide semiconductor layer;a source electrode and a drain electrode over the first oxide semiconductor layer;a gate insulating layer over the first oxide semiconductor layer; anda gate electrode over the gate insulating layer; and a third transistor over the interlayer insulating film, the third transistor comprising:
a second oxide semiconductor layer, wherein the gate electrode of the first transistor is electrically connected to one of the source electrode and the drain electrode of the second transistor, and wherein the first oxide semiconductor layer comprises a region overlapping with both of the gate electrode of the second transistor and one of the source electrode and the drain electrode of the second transistor.