As the insulating film provided between the substrate 10 and the metal film 11, a single layer structure of an insulating film at least having oxygen or nitrogen such as silicon oxide (SiOx), silicon nitride (SiNx), a silicon oxide film containing nitrogen (SiOxNy film) (x>y) (x and y are positive integers), or a silicon nitride film containing oxygen (SiNxOy film) (x>y) (x and y are positive inte