Patent ID: 8872171

Claim:
A semiconductor device comprising: a gate electrode over a substrate having an insulating surface; a silicon nitride film over the gate electrode; a first insulating film over the silicon nitride film, the first insulating film comprising silicon and oxygen; an oxide semiconductor layer on and in contact with the first insulating film; a second insulating film on and in contact with the oxide semiconductor layer, the second insulating film comprising silicon and oxygen; a source electrode and a drain electrode over the second insulating film; and a silicon oxide film on and in contact with the source electrode, the drain electrode and the second insulating film, the silicon oxide film being continuously formed from a top surface of the source electrode to a top surface of the drain electrode; wherein the source electrode and the drain electrode are electrically connected to the oxide semiconductor layer through, respectively, a first opening and a second opening in the second insulating film, wherein the first opening and the second opening each define a top portion of the oxide semiconductor layer, each of the top portions being not covered with the second insulating film and an entirety of each of the top portions overlapping the gate electrode, and wherein a channel formation region of the oxide semiconductor layer is interposed between the first insulating film and the second insulating film.