FABRICATION OF SEMICONDUCTOR DEVICE

PURPOSE:To lower the ion implantation energy and to increase the impurity concentration by performing a heat treatment under specified conditions in a nitrogen atmosphere and forming a well by diffusing the ion implanted impurities from a buries layer to an epitaxial layer. CONSTITUTION:A predetermined region of a semiconductor substrate is subjected to ion implantation thus forming a buried layer. A substrate material is then grown epitaxially on the buried layer 13 thus forming an epitaxial layer 13. It is then subjected to heat treatment in a nitrogen atmosphere at 1100-1200 deg.C for 3-5 hours to diffuse the impurities from the buried layer 13 to the surface of the epitaxial layer 13 or a deep position of the semiconductor substrate 10 thus forming an n-type well 15. Since the buried layer 13 can be formed at a shallow position of the semiconductor substrate 10 by ion implantation of P, implantation energy can be decreased and damage on the semiconductor substrate 10 can be reduced.