PURPOSE: To obtain a second epitaxial growth layer which has an improved flatness by using selective epitaxial growth, instead of isotropic etching, for silicon and thereby eliminating troubles specific to isotropic etching.

CONSTITUTION: A p-type epitaxial layer 12 of mesa shape is formed on a semiconductor substrate 1 by a selective epitaxial growth method. A mask layer 13 is formed on the uppermost layer of the mesa epitaxial layer 12. A silicon film containing Sb is deposited on exposed parts of the semiconductor substrate 1 and the mesa p-type epitaxial layer 12. The collector 15 of a transistor is formed by heat treatment, and then an n-type epitaxial layer 16 is formed. The resultant device is then subjected to a 'mecha-chemical' polishing process involving chemicals, which is so designed that the polishing operation is automatically stopped when the mask layer 13 is reached. This obtains a semiconductor element which enables higher degrees of integration, making it possible to manufacture integrated circuits having a high breakdown voltage.