An insulation film whose requisite constituent elements are first elements and a second element. The first elements include B, P, O and Fe. The second element can generate cations whose hexa-coordinated ion radius, defined by Shannon, R. D., is 0.073 nm or more, and which are bivalent or more. Since the second element having a large ion radius is incorporated into network formers made from the first elements, it is possible to improve the heat resistance of the insulation film.