holes u2295 from the p layer 11 can be smoothly pulled out through the n layer 121 and n layer 122 at the time of turn off the turn off time can be also reduced the n layer 121 functions as a stopper of the depletion layer extending in the n layer 12 a film thickness of the n layer can be made thin and the on voltage can be reduced in the compound semiconductor device according to the invention as described above since the current can be turned on or off by the insulating gate no malfunction occurs so that a high performance of the electric power converting apparatus can be accomplished fig1 shows an embodiment of an inverting apparatus to control a motor in the case where the compound semiconductor device of the invention is used as a switching device fig1 shows a 3 phase inverting apparatus to control a 3 phase inductive motor im and its fundamental circuit has a construction such that three serial circuits each comprising two switching devices are connected in parallel between dc terminals t 1 and t 2 and ac terminals t 3 t 4 and t 5 are led out from the middle points of those three serial circuits snubber circuits s each comprising a flywheel diode fd a snubber diode sd a snubber resistor sr and a snubber capacitor sc are connected in parallel to switching devices sw 1 sw 2 sw 3 sw 4 sw 5 and sw 6 it is.