PURPOSE: To adequately adjust the impurity density of each region surface by a method wherein a heat treatment is performed in a wet atmosphere, after etching the other region surface in the state of covering one region with a mask material.
CONSTITUTION: The impurity of boron 9 is introduced through the mask for boron diffusion into the surface of an epitaxial layer 3 at a density high than at the time of normal formation of a well. After forming an Si, an SiO2 film, or an Si nitride film 10, the vapor chemical precipitation film on a well part is etched, thus a part of an epitaxial layer 3 is exposed, and the surface thereof is etched resulting in the removal of the surface layer wherein boron is introduced at a high density. By performing a heat treatment in a wet atmosphere, the impurity of boron is extended and diffused deep inside, thus a P-base layer 6 is formed, and a P isolation 7 and a P-well 8 are formed.
ANZAI NORIO
MATSUDA TOSHIHIRO
