PURPOSE: To improve the adhesive strength of a metallic frame and a molding resin, and to enhance heat-dissipating characteristics by forming irregularities on the radiating surface of the metallic frame while executing blast treatment.

CONSTITUTION: In a semiconductor device having a shape that the radiating surface (the rear) of a metallic frame 1 on which a semiconductor chip 2 is mounted is electrically insulated by a resin 3, irregularities are formed to the radiating surface M of the metallic frame 1 while blast treatment is executed. The radiating surface M of the metallic frame 1 for a discrete power element is stamping-worked (irregularly-worked) on one surface in size of the square of 0.1mm depth and 0.5mm width, and roughened-surface working is executed to the surface of the radiating surface M through blast treatment. In this case, the working shape of irregularities may take a V shape, or a plane shape may take a striped, polygonal, circular or rectangular shape, etc.