PURPOSE: To effectively prevent the introduction of water from the exterior by forming slits at a heat dissipating plate sealed with resin and forming a resin barrier passing through the slits.

CONSTITUTION: Three slits 151W153 are arranged along the widthwise direction of a heat dissipating plate 11 at the part sealed with resin 13 between the semiconductor element section at the center of the plate 11 and the exposed part, and resin barriers are formed elevationally through the respective slits with the resin 13. Thus, the introduction passage of the water can be largely prolonged to increase the shielding effect.