Patent ID: 8664658

Claim:
A semiconductor device comprising: a first transistor, the first transistor being an n-channel transistor, and a first gate of the first transistor being electrically connected to a first wiring to which a first signal is supplied; a second transistor, the second transistor being a p-channel transistor, a first gate of the second transistor being electrically connected to a second wiring to which a second signal is supplied, and one of a source and a drain of the second transistor being electrically connected to one of a source and a drain of the first transistor; an insulating film over the first transistor and the second transistor; and a third transistor over the insulating film, wherein one of the first transistor and the second transistor comprises a second gate, wherein the second gate is electrically connected to one of a source and a drain of the third transistor, and wherein a channel formation region of the third transistor comprises an oxide semiconductor layer.