PURPOSE: To improve heat dissipation and to eliminate the crack of a semiconductor element by opening a trapezoidal recess on an element substrate, so burying reinforcing metal of metal having high thermal conductivity that the rear side of the element becomes flat, and soldering the rear face to a heat sink tab.

CONSTITUTION: A trapezoidal recess 8 inclined at 45° with respect to a vertical direction on the tapered wall of a converted shape from the end of a part directly under a heated part 2 provided at the surface 1a of a semiconductor element 1 is opened, metal having high thermal conductivity, such as silver or gold is so buried in the recess 8 that the rear face 1b of the element 1 becomes flat by plating, as a reinforcing metal 9. The thus reinforced element 1 is die bonded by solder to a heat sink tab 4 at the rear side 1b by lead solder 5. Further, fine metal wirings 7 are connected to external leads 6 to be electrically connected. Accordingly, heat dissipation is remarkably improved, and even if the thickness of the element is reduced, it is not cracked.