As the gate insulating film 4604, a single layer structure or a stacked-layer structure of insulating films containing nitrogen or oxygen such as silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiOxNy) (x>y), or silicon nitride oxide (SiNxOy)(x>y) can be employed by a sputtering method, an LPCVD method, a plasma CVD method, or the like.