Patent ID: 8828811

Claim:
A method for manufacturing a semiconductor device, comprising the steps of: forming a gate electrode layer; forming a first gate insulating film over the gate electrode layer; forming an oxide semiconductor film by sputtering method over the first gate insulating film so as to overlap with the gate electrode layer, wherein a substrate temperature is set to temperatures higher than or equal to 100° C. and lower than or equal to 600° C. during forming the oxide semiconductor film; performing heat treatment on the oxide semiconductor film to remove a hydrogen atom in the oxide semiconductor film; performing oxygen doping treatment on the oxide semiconductor film to supply an oxygen atom into the oxide semiconductor film after the heat treatment; forming a source electrode layer and a drain electrode layer which are electrically connected to the oxide semiconductor film; and forming a second insulating film over the oxide semiconductor film, the source electrode layer, and the drain electrode layer so as to be in contact with the oxide semiconductor film.