A semiconductor device has a semiconductor substrate having an upper main surface and a lower main surface. The semiconductor substrate includes a drain layer, a main base region, an underpad base region and a source region. The semiconductor device includes a first main electrode connected to the main base regions and the source region and not connected to the underpad base region, a gate electrode opposed to a channel region in the main base region interposed between the drain layer and the source region with a gate insulating film provided therebetween, a conductive gate pad opposed to an exposed surface of the underpad base region in the upper main surface with an insulating layer interposed therebetween and the conductive gate pad is connected to the gate electrode, and a second main electrode connected to the lower main surface.