Patent ID: 8395156

Claim:
A display device comprising: a substrate; a pixel portion including a single-gate transistor, the single-gate transistor comprising: a first gate electrode over the substrate; a gate insulating layer over the first gate electrode; a first semiconductor layer over the gate insulating layer, the first semiconductor layer comprising: a first microcrystalline semiconductor region over the gate insulating layer; and a first amorphous semiconductor region over the first microcrystalline semiconductor region, a pair of first wirings over the first amorphous semiconductor region; and an insulating layer over the pair of first wirings and the first amorphous semiconductor region, a driver circuit including a dual-gate transistor, the dual-gate transistor comprising: a second gate electrode over the substrate; the gate insulating layer over the second gate electrode; a second semiconductor layer over the gate insulating layer, the second semiconductor layer comprising: a second microcrystalline semiconductor region over the gate insulating layer; and a pair of second amorphous semiconductor regions over the second microcrystalline semiconductor region, a pair of second wirings over the pair of second amorphous semiconductor regions; the insulating layer over the pair of second wirings and the second microcrystalline semiconductor region; and a back gate electrode over the insulating layer, wherein the insulating layer in the pixel portion is over and in contact with the first amorphous semiconductor region in a first region that overlaps with a region between the pair of the first wirings, wherein the insulating layer in the pixel portion is not in contact with the first microcrystalline semiconductor region in the first region, and wherein the insulating layer in the driver circuit is over and in contact with the first amorphous semiconductor region and the second microcrystalline semiconductor region in a second region that overlaps with a region between the pair of the second wirings.