PURPOSE: To obtain a semiconductor device using a laminated substrate for realizing a high breakdown voltage and a low series resistance simultaneously by forming a groove for diffusing elements with anisotropic etching simultaneously with the groove for separating elements and by diffusing impurities through the groove for diffusing elements for directly diffusing the impurities to a deep region without going through heat treatment at high temperature for a long time.

CONSTITUTION: In a manufacture of a semiconductor device using a laminated substrate having an insulating layer 2b at least at one region of the laminated interface, a mask for etching which is equipped with a window for separating elements 5 and a window for element region 20 which is narrower than the window 5 are formed on the surface of a semiconductor substrate 2 related to the lamination and then anisotropic etching is performed for forming a groove for separating elements 6 reaching the insulation layer 2b and a groove for diffusing elements which are shallower than the depth of the groove 6 simultaneously. Then, after a dielectric separation layer is formed by burying a dielectric 3a within the groove for separating elements 6, impurities are diffused into a deep region within the semiconductor substrate 2 through the groove for diffusion elements 21, thus forming an element activation region. For example, phosphor is diffused from the inner surface of the groove for diffusion elements 21 for forming an N+ collector wall diffusion layer 23.