Semiconductor ic with dual groove isolation

Abstract

A bipolar type of semiconductor integrated circuit device is provided with U-shaped grooves which are formed by cutting a main surface of a semiconductor body to form isolation regions between bipolar transistors. A silicon oxide film can be formed in the U-shaped grooves by thermal oxidation simultaneously with the formation of a silicon oxide film used to form isolation regions between each collector contact region and base region. No separate step is needed for forming the silicon oxide film between the collector contact region and the base region. The thickness of the silicon oxide film can be controlled, and has a sufficient thickness even at its two edges, i.e., at its boundaries with the U-shaped grooves, so that the bipolar transistors exhibit good electrical characteristics. Namely, the collector resistance thereof does not increase, and the breakdown voltage at the pn junction between the collector region and the base region does not decrease. The U-shaped grooves can each comprise narrow and deep sub-grooves, with thick oxide films formed on the surfaces of the sub-grooves and a thick oxide film formed on a surface of an area between the sub-grooves, and with wiring formed on the oxide on the area between the sub-grooves.