Patent ID: 7993991

Claim:
A manufacturing method of a thin film transistor, comprising the steps of: forming a first conductive film; forming an insulating film over the first conductive film; forming a semiconductor film over the insulating film; forming an impurity semiconductor film over the insulating film; forming a second conductive film over the impurity semiconductor film; forming a first resist mask over the second conductive film; first etching the insulating film, the semiconductor film, the impurity semiconductor film, and the second conductive film using the first resist mask to expose at least a surface of the first conductive film; second etching a portion of the first conductive film to form a gate electrode layer in such a manner that a width of the gate electrode layer is narrower than a width of the insulating film; forming a second resist mask over the second conductive film; and third etching the second conductive film, the impurity semiconductor film, and a part of the semiconductor film using the second resist mask to form source and drain electrode layers, source and drain region layers, and a semiconductor layer.