Patent ID: 7588970

Claim:
A method for manufacturing a semiconductor device, the method comprising the steps of: forming a semiconductor layer over a substrate having an insulating surface, forming an insulating film over the semiconductor layer, forming a first conductive film over the insulating film, forming a second conductive film over the first conductive film, forming a resist pattern over the second conductive film, the resist pattern having a first portion and a second portion with a thickness thinner than that of the first portion, forming a gate electrode by selectively etching the first conductive film and the second conductive film, the gate electrode having a first portion and a second portion with a thickness thinner than that of the first portion, wherein the first portion of the gate electrode includes the first conductive film and the second conductive film, and wherein the second portion of the gate electrode includes the first conductive film, forming first impurity regions in the semiconductor layer on both sides of a channel formation region by injecting an impurity element into the semiconductor layer using the first portion and the second portion of the gate electrode as a mask, and forming a second impurity region in the semiconductor layer in a region overlapped with the second portion of the gate electrode by injecting an impurity element into the semiconductor layer through the second portion of the gate electrode.