PURPOSE:To obtain high heat dissipating property, to make it possible to implement a low cost and a thin configuration, and to obtain excellent electric insulation, by constituting a base material by a molybdenum plate, materials comprising films of copper or copper alloy, which are provided on the upper and lower surface of the molybdenum plates, and an electric insulating ceramic thin film formed on one surface of the base material. CONSTITUTION:The base material of a substrate is formed by laminating copper or copper-alloy films 2 and 3 having high heat conductivity on the upper and lower surfaces of a molybdenum plate 1 having a small thermal expansion coefficient. As a forming method, a cladding method such as cold welding, hot welding, explosion molding and the like is suitable. An electric insulating ceramic thin film 4 is formed on one surface of said base material, e.g., on the surface of the copper or copper-alloy film 2. Thus a substrate is formed. As the electric insulating ceramic thin film 4, there are the following materials : oxides such as, e.g., Al2O3, Y2O3, ZrO2, TiO2 and the like and composite oxides, in which said oxides are the main components; nitrides of Si3N4, AlN and the like and composite nitrides, in which said nitrides are the main components; diamond-or pseudo-diamond-state carbon or the mixed material of the carbon; and the like.