Patent ID: 8445905

Claim:
A semiconductor device comprising: a pixel portion over a substrate, the pixel portion comprising a first transistor; and a driver circuit portion over the substrate, the driver circuit portion comprising a second transistor, wherein the first transistor comprises: a first gate electrode layer over the substrate; a first gate insulating layer over the first gate electrode layer; a first oxide semiconductor layer including a first channel region over the first gate insulating layer; and a first source electrode layer and a first drain electrode layer over the first oxide semiconductor layer, wherein the second transistor comprises: a second gate electrode layer over the substrate; a second gate insulating layer over the second gate electrode layer; a second oxide semiconductor layer including a second channel region over the second gate insulating layer; and a second source electrode layer and a second drain electrode layer over the second oxide semiconductor layer, wherein the first channel region includes a first region including excess oxygen, wherein the second channel region includes a second region including excess oxygen, and wherein a material of the second source electrode layer and the second drain electrode layer is different from a material of the first source electrode layer and the first drain electrode layer.