A semiconductor device includes a semiconductor chip which can be a heat-generating semiconductor chip or a semiconductor relay substrate in which an integrated circuit or wiring is built in. A sintered-silver-coated film is adhered on a surface layer part of the semiconductor substrate, interposed by a silicon oxide film. A heat-dissipating fin (heat sink), which may be copper or aluminum, is bonded on the sintered-silver-coated film, interposed by an adhesive layer.