Patent ID: 7776664

Claim:
A method of manufacturing a semiconductor device, comprising: forming a gate electrode over a light-transmitting substrate; forming a gate insulating film over the gate electrode; forming a first semiconductor film over the gate insulating film; forming a second semiconductor film including an impurity element imparting one conductivity type over the first semiconductor film; forming a first photoresist pattern over the second semiconductor film with use of a multitone photomask; etching the first semiconductor film and the second semiconductor film using the first photoresist pattern as a mask; forming a second photoresist pattern by processing the first photoresist pattern; forming a conductive film over the gate insulating film, the second semiconductor film, and the second photoresist pattern; and forming a source electrode and a drain electrode by removing the second photoresist pattern and a portion of the conductive film formed over the second photoresist pattern at the same time.