Patent ID: 7883943

Claim:
A method for manufacturing a thin film transistor, comprising: forming a first conductive film over a substrate; forming an insulating film over the first conductive film; forming a semiconductor film over the insulating film; forming an impurity semiconductor film over the semiconductor film; forming a second conductive film over the impurity semiconductor film; forming a first resist mask including a recessed portion over the second conductive film and including at least one opening portion; exposing at least a surface of the first conductive film by performing first etching on the insulating film, the semiconductor film, the impurity semiconductor film, and the second conductive film using the first resist mask; forming a gate electrode layer by performing second etching in which a part of the first conductive film is side-etched; after forming the gate electrode layer, forming a second resist mask by making the first resist mask to be reduced to expose a part of the second conductive film, which overlaps with the recessed portion of the first resist mask; and forming a source and drain electrode layer, a source and drain region, and a semiconductor layer by performing third etching on the second conductive film, the impurity semiconductor film, and a part of the semiconductor film using the second resist mask.