Patent ID: 7459354

Claim:
A method for manufacturing a semiconductor device comprising the steps of: forming an insulating film comprising silicon oxide nitride over a substrate by a plasma CVD process; forming a first semiconductor film comprising silicon having an amorphous structure over the insulating film; performing a heating process on the first semiconductor film to form a second semiconductor film; irradiating laser light to the second semiconductor film to form a third semiconductor film having a plurality of convexes; irradiating intense light to the third semiconductor film to form a fourth semiconductor film; patterning the fourth semiconductor film to form at least one semiconductor layer; forming a gate dielectric film over the fourth semiconductor film; forming a gate electrode over the fourth semiconductor film; forming a first concentration impurity region by doping the fourth semiconductor film; forming a second concentration impurity region having a region that overlaps the gate electrode by doping the fourth semiconductor film; and performing a heating process in a nitrogen atmosphere to activate an impurity element added to the first concentration impurity region and the second concentration impurity region.