a semiconductor device includes a semiconductor substrate having at least three semiconductor layers of alternately different conductivity types between a pair of principal surfaces . a pair of main electrodes are kept in low - resistance contact with the outermost ones of the semiconductor layers . a surface - passivation insulating film is provided on an exposed surface of the semiconductor substrate . a resistive material sheet is provided on the insulating film and connected electrically to semiconductor layers having their potentials substantially equal to the main electrodes .