Patent ID: 8324626

Claim:
A semiconductor device comprising: a pixel portion including a first thin film transistor over a substrate; and a driver circuit portion including a second thin film transistor over the substrate, the first thin film transistor comprising: a first gate electrode layer; a first gate insulating layer over the first gate electrode layer; a first semiconductor layer over the first gate insulating layer; and a first source electrode layer and a first drain electrode layer over the first semiconductor layer, the second thin film transistor comprising: a second gate electrode layer; a second gate insulating layer over the second gate electrode layer; a second semiconductor layer over the second gate insulating layer; and a second source electrode layer and a second drain electrode layer over the second semiconductor layer, wherein each of the first gate electrode layer, the first gate insulating layer, the first semiconductor layer, the first source electrode layer, and the first drain electrode layer is capable of transmitting light, wherein a material of the first gate electrode layer is different from a material of the second gate electrode layer, wherein resistance of the second gate electrode layer is lower than that of the first gate electrode layer, wherein a material of the first source electrode layer and the first drain electrode layer is different from a material of the second source electrode layer and the second drain electrode layer, and wherein resistance of the second source electrode layer and the second drain electrode layer is lower than that of the first source electrode layer and the first drain electrode layer.