Abstract: The present invention is directed to power semiconductor devices and, more particularly, to a semiconductor device with a static induction buffer structure which reduces the resistance of a buffer layer, enhances the injection efficiency of holes from the anode and permits the application of a high-intensity electric field across the cathode and anode, and a semiconductor device with a drift buffer structure in which an impurity density (concentration) gradient is set in a buffer layer to generate an internal electric field for holes to enhance the injection efficiency of holes from the anode and increase the electron storage efficiency or and impurity density (concentration) gradient is set in an anode region to generate an internal electric field for electrons and a high-intensity electric field can be applied across the cathode and anode.