Method for manufacturing semiconductor device

A method for manufacturing a semiconductor device, comprising the steps of:

• forming a gate electrode layer;
• forming a gate insulating film over the gate electrode layer;
• forming an oxide semiconductor film over a region of the gate insulating film, which overlaps with the gate electrode layer;
• forming a source electrode layer and a drain electrode layer electrically connected to the oxide semiconductor film;
• forming an insulating film over the oxide semiconductor film, the source electrode layer, and the drain electrode layer and in contact with the oxide semiconductor film;
• removing water or hydrogen from the insulating film by performing a first heat treatment on the insulating film;
• and
• supplying oxygen to the insulating film by performing a first oxygen doping treatment on the insulating film after performing the first heat treatment.

A method for manufacturing a semiconductor device, comprising the steps of:

• forming a gate electrode layer;
• forming a gate insulating film over the gate electrode layer;
• removing water or hydrogen from the gate insulating film by performing a first heat treatment on the gate insulating film;
• supplying oxygen to the gate insulating film by performing a first oxygen doping treatment on the gate insulating film after performing the first heat treatment;
• forming an oxide semiconductor film over a region of the gate insulating film, which overlaps with the gate electrode layer;
• forming a source electrode layer and a drain electrode layer electrically connected to the oxide semiconductor film;
• forming an insulating film in contact with the oxide semiconductor film and over the oxide semiconductor film, the source electrode layer, and the drain electrode layer;
• removing water or hydrogen from the insulating film by performing a second heat treatment on the insulating film;
• and
• supplying oxygen to the insulating film by performing a second oxygen doping treatment on the insulating film after performing the second heat treatment.