Patent ID: 8648343

Claim:
A semiconductor device comprising: a pixel portion over a substrate, the pixel portion comprising a first transistor and a pixel electrode layer; and a driver circuit over the substrate, the driver circuit comprising a second transistor, wherein the first transistor comprises: a first gate electrode layer over the substrate; a gate insulating layer over the first gate electrode layer; a first oxide semiconductor layer over the gate insulating layer; a first oxide insulating layer in contact with a part of the first oxide semiconductor layer; and a first source electrode layer and a first drain electrode layer over and in contact with both the first oxide insulating layer and the first oxide semiconductor layer, wherein the second transistor comprises: a second gate electrode layer over the substrate; the gate insulating layer over the second gate electrode layer; a second oxide semiconductor layer over the gate insulating layer; and a second source electrode layer and a second drain electrode layer over the second oxide semiconductor layer, wherein the first gate electrode layer, the gate insulating layer, the first oxide semiconductor layer, the first oxide insulating layer, the first source electrode layer, the first drain electrode layer and the pixel electrode layer have a light-transmitting property, 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.