A semiconductor device comprising: a first substrate on which a semiconductor element is mounted; a positive-side power terminal, a negative-side power terminal, an output-side power terminal, positive-side control terminals and negative-side control terminals connected to the semiconductor element (2a,2b); a heat-dissipating plate; an insulating layer disposed between and electrically insulating the first substrate and the heat-dissipating plate; and molding resin that molds the first substrate, the heat-dissipating plate, the positive-side power terminal, the negative-side power terminal, the output-side power terminal, the positive-side control terminals, and the negative-side control terminals and the insulating layer, the heat-dissipating plate being rectangular and having first and second edges opposed to each other and a first surface opposite to the insulating layer, the first surface being exposed from the molding resin, and the insulating layer having first and second curved portions respectively facing the opposing first and second edges of the heat-dissipating plate, each curved portion being bent towards the first surface along a side of the heat-dissipating plate, wherein end portions of the insulating layer are located in the molding resin, the curved portions have a length shorter than a thickness of the heat-dissipating plate, the positive-side power terminal, the negative-side power terminal, the output-side power terminal, the positive-side control terminals and the negative-side control terminals are exposed from the resin, characterized in that the curved portions of the insulating layer are not in contact with the respective sides of the heat-dissipating plate and are located farther from the respective sides of the heat-dissipating plate as the curved portions approach the first surface. a first substrate on which a semiconductor element is mounted; a positive-side power terminal, a negative-side power terminal, an output-side power terminal, positive-side control terminals and negative-side control terminals connected to the semiconductor element (2a,2b); a heat-dissipating plate; an insulating layer disposed between and electrically insulating the first substrate and the heat-dissipating plate; and molding resin that molds the first substrate, the heat-dissipating plate, the positive-side power terminal, the negative-side power terminal, the output-side power terminal, the positive-side control terminals, and the negative-side control terminals and the insulating layer, the heat-dissipating plate being rectangular and having first and second edges opposed to each other and a first surface opposite to the insulating layer, the first surface being exposed from the molding resin, and the insulating layer having first and second curved portions respectively facing the opposing first and second edges of the heat-dissipating plate, each curved portion being bent towards the first surface along a side of the heat-dissipating plate, wherein end portions of the insulating layer are located in the molding resin, the curved portions have a length shorter than a thickness of the heat-dissipating plate, the positive-side power terminal, the negative-side power terminal, the output-side power terminal, the positive-side control terminals and the negative-side control terminals are exposed from the resin, characterized in that the curved portions of the insulating layer are not in contact with the respective sides of the heat-dissipating plate and are located farther from the respective sides of the heat-dissipating plate as the curved portions approach the first surface.