Abstract: This invention provides devices each of which has at least one bipolar transistor and at least one MOS transistor, both formed on a substrate. This invention also provides their fabrication process. Each device is constructed of epitaxial layers of a first and second conductivity types, surfaces of said epitaxial layers being partly exposed, at least one MOS transistor formed in the epitaxial layer of the first conductivity type, and at least one bipolar transistor formed in the epitaxial layer of the second conductivity type. Its fabrication process comprises the steps of forming the epitaxial layer of the second conductivity type on the semiconductor substrate, forming the epitaxial layer of the first conductivity type on a part of the epitaxial layer of the second conductivity type, forming the bipolar transistor in the epitaxial layer of the second conductivity type and then forming the MOS transistor in the epitaxial layer of the first conductivity type.

Abstract: A method of forming electric conductive patterns comprising the steps of forming first conductive patterns on a semiconductor substrate directly or through an insulating layer with first insulating film being formed thereon, selectively forming second conductive patterns, forming insulation layers on side surfaces of said second conductive patterns, thereby electrically insulating said second conductive patterns from said first conductive patterns through said insulation layers in a self-aligned manner. An semiconductor device having electric conductive patterns formed by above-mentioned method.