Preßgespritztes power device and method of manufacturing the power device preßgespritzten

A semiconductor device includes a semiconductor chip that generates heat during operation, a pair of heat sinks for cooling the chips, and a mold resin, in which the chip and the heat sink is embedded. The thickness t1 of the chip and the thickness t2 of the heat sink, which is connected using a solder to the chip satisfy the relationship t2 / t1> = 5. Furthermore satisfy the thermal expansion coefficient alpha 1 of the heat sink and the thermal expansion coefficient alpha 2 of mold resin relationship of 0.5 alpha2 / alpha1 1.5. In addition, has the surface of the chip, which is opposed to the solder, a roughness Ra, which satisfies the relationship Ra 500nm. In addition, the solder is a solder based on Sn, so as to suppress the relaxation of a compressive stress in the chip, which is caused by the creeping of the solder.