Patent ID: 8502220

Claim:
A semiconductor device comprising: a driver circuit portion comprising a first thin film transistor and a pixel portion comprising a second thin film transistor, the first thin film transistor and the second thin film transistor each comprising: a gate electrode layer over a substrate; a gate insulating layer over the gate electrode layer; an oxide semiconductor layer over the gate insulating layer, the oxide semiconductor layer overlapping the gate electrode layer; a first conductive layer over the oxide semiconductor layer, the first conductive layer being electrically connected to the oxide semiconductor layer; a second conductive layer over the oxide semiconductor layer, the second conductive layer being electrically connected to the oxide semiconductor layer; an oxide insulating layer over the oxide semiconductor layer, the first conductive layer and the second conductive layer, the oxide insulating layer being in contact with a first top surface of an end portion of the oxide semiconductor layer and a second top surface of the oxide semiconductor layer between the first conductive layer and the second conductive layer; a pixel electrode layer over the oxide insulating layer; and a liquid crystal layer over the pixel electrode layer, wherein the first thin film transistor further comprises a third conductive layer which overlaps with the oxide semiconductor layer over the oxide insulating layer, wherein the second conductive layer of the second thin film transistor is electrically connected to the pixel electrode layer, and wherein the oxide semiconductor layer includes a region in an oxygen-excess state.