Patent ID: 7821002

Claim:
A semiconductor device comprising: a semiconductor layer formed on an insulating surface; a gate electrode formed over the semiconductor layer; a first insulating layer provided between the semiconductor layer and the gate electrode; and a second insulating layer over the gate electrode, wherein the first insulating layer comprises a first region having a first film thickness and a second region having a second film thickness which is thicker than the first film thickness, wherein the second region having the second film thickness covers an end portion of the semiconductor layer which the gate electrode overlaps, wherein the first insulating layer comprises a third insulating layer and a fourth insulating layer over the third insulating layer and the semiconductor layer, and wherein a side surface of the semiconductor layer is inclined at a first angle with respect to the insulating surface, a side surface of the third insulating layer over the side surface of the semiconductor layer is inclined at a second angle with respect to the insulating surface, and a side surface of the third insulating layer is positioned on the side surface of the semiconductor layer.