Semiconductor device and method for manufacturing semiconductor device

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

• forming a semiconductor film;
• forming an electrode electrically connected to the semiconductor film;
• forming a gate insulating film over the semiconductor film, the gate insulating film having a stacked structure comprising a first insulating film and a trap film;
• forming a gate electrode over the gate insulating film;
• and
• keeping a potential of the gate electrode higher than a potential of the electrode for one second or longer at a temperature higher than or equal to 125° C. and lower than or equal to 450° C., so that electrons are trapped in the trap film and a threshold value is shifted in a positive direction,
• wherein the trap film is an insulating film containing nitrogen and silicon.

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

• forming a semiconductor film;
• forming an electrode electrically connected to the semiconductor film;
• forming a gate insulating film over the semiconductor film, the gate insulating film having a stacked structure comprising a first insulating film and a trap film;
• forming a gate electrode over the gate insulating film;
• and
• keeping a potential of the gate electrode lower than a potential of the electrode for one second or longer at a temperature higher than or equal to 125° C. and lower than or equal to 450° C., so that holes are trapped in the trap film and a threshold value is shifted in a negative direction,
• wherein the trap film is an insulating film containing nitrogen and silicon.