Method for forming an impurity region in semiconductor devices by

Abstract

The invention discloses a method including the following processes (a) through (c) for forming impurity regions in a semiconductor device (a) a process that forms at least one second conductive type impurity-doped region by doping second conductive type impurity selectively to a predetermined region of a first conductive type semiconductor layer constituting a semiconductor substrate, (b) a process that forms on the surface of the semiconductor substrate a diffusion mask having a first opening for exposing at least one of the second conductive type impurity regions and having a second opening for exposing a part adjacent to at least one of the second conductive type impurity regions, (c) a process that forms the second conductive type impurity region and a low concentration second conductive type impurity region being in contact with the former by out-diffusing through the first opening the second conductive type impurity of the second conductive type impurity region and re-doping the out-diffused impurity through the second opening to the first conductive type semiconductor layer. According to the method, an impurity region having a high breakdown voltage is formed by simple processes to have a smooth lateral concentration profile by means of vaporization and re-diffusion of the impurity previously doped to a semiconductor layer.