Abstract: An improved structure of a heat sink for power semiconductors is provided in the form of a U-shaped heat sink extruded from an aluminum material. The heat sink has a number of individual and oppositely juxtaposed heat dissipation fins formed along the inside and the outside surfaces of the two lateral walls thereof. The heat sink has two fastener plates slanting downward respectively from inner surfaces of the lateral walls and extending an appropriate length. A pair of fastener tabs are individually punched out and bent inward in opposed juxtaposition at the rear end of the two lateral walls. The heat sink includes heat dissipation fins that are directly formed continuously along opposing sides of the two lateral walls of a U-shaped heat sink.