PURPOSE: To protect resin and semiconductor chip from mechanical destruction even in case there are rugged potions and dust on the surface of heat dissipating plate by forming a cut-away part which does not reach the mounting hole to the one end part of fixed contact surface for heat dissipating plate or substrate.

CONSTITUTION: At the upper head region of resin 21 to be used as the external case of semiconductor device, a mounting hole 16 which is bored through the fixed contact surface, for example, for the heat dissipating plate or substrate from the surface thereof is formed. A cut-away part 22 is formed to the fixed contact surface region which does not reach the mounting hole from the upper end part of such resin 21. In this case, distance (a) from the mounting hole 16 to the cut-away part 22 is set, for example, to about 0.3mm and the lead terminal 14 is caused to not to be floated by this principle at the time of fixing the resin 21. The distance (b) of concaved part of cut-away portion 22 is set to a munute size of 0.1mm and thereby heat radiation efficiency of semiconductor device can be protected from drastic lowering.