Method for manufacturing semiconductor device

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

• forming an island-like semiconductor film over a substrate having an insulating surface;
• oxidizing a surface of the island-like semiconductor film to form a first insulating film which is any one of an oxide film, an oxide film including nitrogen, and a film including a suboxide on the surface of the island-like semiconductor film;
• forming a semiconductor film on a region which is a part of the first insulating film;
• nitriding the surface of the island-like semiconductor film to form a second insulating film which is any one of a nitride film including oxygen, a nitride film, and a film including a subnitride on the surface of the island-like semiconductor film;
• forming a third insulating film over the first insulating film and the second insulating film;
• forming a gate electrode over the third insulating film;
• adding an impurity element imparting one conductivity type to the island-like semiconductor film and the semiconductor film using the gate electrode as a mask;
• and
• heating the island-like semiconductor film and the semiconductor film to activate the impurity element,
• wherein the first insulating film disappears at least partly by heating the island-like semiconductor film and the semiconductor film.

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

• forming an island-like semiconductor film over a substrate having an insulating surface;
• nitriding a surface of the island-like semiconductor film to form a first insulating film which is any one of a nitride film including oxygen, a nitride film, and a film including a subnitride on the surface of the island-like semiconductor film;
• forming a semiconductor film on a region which is a part of the first insulating film;
• oxidizing the surface of the island-like semiconductor film to form a second insulating film which is any one of an oxide film, an oxide film including nitrogen, and a film including a suboxide on the surface of the island-like semiconductor film;
• forming a third insulating film over the first insulating film and the second insulating film;
• forming a gate electrode over the third insulating film;
• adding an impurity element imparting one conductivity type to the island-like semiconductor film and the semiconductor film using the gate electrode as a mask;
• and
• heating the island-like semiconductor film and the semiconductor film to activate the impurity element,
• wherein the first insulating film disappears at least partly by heating the island-like semiconductor film and the semiconductor film.

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

• forming an island-like semiconductor film over a substrate having an insulating surface;
• nitriding a surface of the island-like semiconductor film to form a first insulating film which is any one of a nitride film including oxygen, a nitride film, and a film including a subnitride on the surface of the island-like semiconductor film;
• forming a semiconductor film on a region which is a part of the first insulating film;
• nitriding the surface of the island-like semiconductor film to form a second insulating film which is any one of a nitride film including oxygen, a nitride film, and a film including a subnitride on the surface of the island-like semiconductor film;
• forming a third insulating film over the first insulating film and the second insulating film;
• forming a gate electrode over the third insulating film;
• adding an impurity element imparting one conductivity type to the island-like semiconductor film and the semiconductor film using the gate electrode as a mask;
• and
• heating the island-like semiconductor film and the semiconductor film to activate the impurity element,
• wherein the first insulating film disappears at least partly by heating the island-like semiconductor film and the semiconductor film.