Patent ID: 8268654

Claim:
A method for manufacturing a semiconductor device, comprising the steps of: forming a transparent conductive film and a first metal film sequentially over a substrate; forming a first resist by using a first photomask which is a multi-tone mask, the first resist having different thicknesses in a first portion and in a second portion; forming a gate electrode by shaping the transparent conductive film and the first metal film with the first resist so that a stack of the transparent conductive film and the first metal film is left in the first portion and only the transparent conductive film is left in the second portion; forming an insulating film over the gate electrode; forming a microcrystalline silicon film as a third semiconductor film over the insulating film by microwave plasma CVD with a frequency of greater than or equal to 1 GHz; forming a first semiconductor film, a second semiconductor film, and a second metal film sequentially over the third semiconductor film; forming a second resist by using a second photomask which is a multi-tone mask, the second resist having different thicknesses in a channel region formation portion and in a source region formation portion and a drain region formation portion; forming a third semiconductor layer, a first semiconductor layer, a second semiconductor layer, and a second metal layer by shaping the third semiconductor film, the first semiconductor film, the second semiconductor film, and the second metal film, respectively, with the second resist; forming a channel region, a source region, a drain region, a source wiring, and a drain wiring of a thin film transistor by etching the third semiconductor layer, the first semiconductor layer, the second semiconductor layer, and the second metal layer; forming a protective film over the thin film transistor; and forming a pixel electrode over the protective film.