PURPOSE: To increase the effect of heat radiation and prevent the production of imperfections due to ionic impurities by providing a heat sink containing a refrigerant on the main surface of a substrate on the side where a semiconductor element is not mounted.

CONSTITUTION: When a heat sink 26 prepared by injecting a refrigerant 28 into a space in a metal can 27 and by sealing the same hermetically is fitted on the main surface of a substrate 29 on the opposite side to an element 21, the heat of the element 21 is cooled by the latent heat of vaporization of the refrigerant through the intermediary of the substrate 29. For the refrigerant, a liquid having the boiling point of 30W150°C is suited, water is effective in particular, and alcohol or fluorocarbon is also used. By this constitution, a small-sized resin- sealed device being highly effective in radiation is obtained. In this device, the refrigerant does not contact directly with the surface of the semiconductor element and therefore aluminum wirings are not corroded by the ionic impurities contained in the refrigerant, whereby high reliability of the device is attained. This structure can be applied also to a metal case.