Patent ID: 7821012

Claim:
A thin film transistor comprising: a gate electrode layer; a first insulating layer over the gate electrode layer; a pair of second insulating layers over the first insulating layer, wherein the pair of second insulating layers is provided apart from each other in a channel length direction and overlaps with at least a part of the gate electrode layer; a pair of microcrystalline semiconductor layers over the pair of second insulating layers, wherein the pair of microcrystalline semiconductor layers is provided apart from each other and in contact with the pair of second insulating layers; an amorphous semiconductor layer over the first insulating layer, the pair of second insulating layers, and the pair of microcrystalline semiconductor layers, wherein a part of the amorphous semiconductor layer is provided between the pair of microcrystalline semiconductor layers; and a pair of impurity semiconductor layers over the amorphous semiconductor layer, wherein the pair of impurity semiconductor layers overlaps with at least a part of the gate electrode layer and is provided apart from each other so as to form a source region and a drain region, wherein the first insulating layer is a silicon nitride layer, and each of the pair of second insulating layers is a silicon oxynitride layer.