A semiconductor device comprising: at least one semiconductor module having a semiconductor element (51a through 56a) functioning as a heater element, a resin mold having a plate shape and covering the semiconductor element, and a heat radiation plate (11, 12) covered by the resin mold, exposed from one surface of the resin mold, insulated from the semiconductor element, and radiating heat generated in the semiconductor element; and a cooler disposed on a surface of the semiconductor module where the heat radiation plate is exposed, providing a refrigerant passage, and promoting radiation of heat from the heat radiation plate (11, 12) by flowing a refrigerant through the refrigerant passage, wherein: the heat radiation plate includes fins (11c, 12c) provided by pulling up a surface of the radiation plate (11, 12) along one direction (y) linearly; and the fins have a tapered shape with an elliptical arc shape curved from a base to a tip, characterized in that the surface of the radiation plate (11, 12) includes a protruding surface of fin portions (11c, 12c) and a recessed surface (11d, 12d); the recessed surface (11d, 12d) is provided by a skived side of the surface of the radiation plate (11, 12); and the protruding surface (11c, 12c) is provided by an inner portion opposite to the skived side; and a skiving direction of the multiple fin portions (11c, 12c) has an acute angle (α) with respect to the refrigerant flow direction, the angle being greater than 0° and not greater than 45°. at least one semiconductor module having a semiconductor element (51a through 56a) functioning as a heater element, a resin mold having a plate shape and covering the semiconductor element, and a heat radiation plate (11, 12) covered by the resin mold, exposed from one surface of the resin mold, insulated from the semiconductor element, and radiating heat generated in the semiconductor element; and a cooler disposed on a surface of the semiconductor module where the heat radiation plate is exposed, providing a refrigerant passage, and promoting radiation of heat from the heat radiation plate (11, 12) by flowing a refrigerant through the refrigerant passage, wherein: the heat radiation plate includes fins (11c, 12c) provided by pulling up a surface of the radiation plate (11, 12) along one direction (y) linearly; and the fins have a tapered shape with an elliptical arc shape curved from a base to a tip, characterized in that the surface of the radiation plate (11, 12) includes a protruding surface of fin portions (11c, 12c) and a recessed surface (11d, 12d); the recessed surface (11d, 12d) is provided by a skived side of the surface of the radiation plate (11, 12); and the protruding surface (11c, 12c) is provided by an inner portion opposite to the skived side; and a skiving direction of the multiple fin portions (11c, 12c) has an acute angle (α) with respect to the refrigerant flow direction, the angle being greater than 0° and not greater than 45°. the heat radiation plate includes fins (11c, 12c) provided by pulling up a surface of the radiation plate (11, 12) along one direction (y) linearly; and the fins have a tapered shape with an elliptical arc shape curved from a base to a tip, characterized in that the surface of the radiation plate (11, 12) includes a protruding surface of fin portions (11c, 12c) and a recessed surface (11d, 12d); the recessed surface (11d, 12d) is provided by a skived side of the surface of the radiation plate (11, 12); and the protruding surface (11c, 12c) is provided by an inner portion opposite to the skived side; and a skiving direction of the multiple fin portions (11c, 12c) has an acute angle (α) with respect to the refrigerant flow direction, the angle being greater than 0° and not greater than 45°.