Semiconductor device with a first parallel pn structure in the active region and a second parallel pn structure in the termination region wherein the depth of the second parallel structure becomes stepwise shallower towards the periphery

Abstract

A superjunction semiconductor device has: a semiconductor substrate of a first conductivity type; a buffer layer of the first conductivity type, provided on a front surface of the semiconductor substrate and having an impurity concentration lower than that of the semiconductor substrate; a drift layer of the first conductivity type, provided on the buffer layer and having an impurity concentration lower than that of the buffer layer; and a parallel pn structure having first column regions of the first conductivity type and second column regions of a second conductivity type repeatedly alternating one another in a direction parallel to the front surface. A subset of the first and second column regions are located in a termination structure portion and have depths that become shallower stepwise towards an end of the semiconductor substrate, where the second column regions are provided with bottoms thereof in the drift layer.