One mask technique for substrate contacting in integrated circuits involving deep dielectric isolation

A one mask technique for making substrate contact from the top surface of an integrated circuit device. A thin ion implanted region of one conductivity type is formed over the entirety of a major surface of the semiconductor substrate. By lithography and etching, a shallow etched region is formed to a depth below the region of the first conductivity type at the substrate surface in an area designated for substitute contacting. A region of a second conductivity type is then formed at the central portion of the etched region. The substrate is then heated to form a buried collector region of the first conductivity type and a portion of the reach-through region of the second conductivity type in the substrate. An epitaxial layer is next formed on the major surface of the substrate. A base region of the second conductivity type for the integrated circuit is then formed. A portion of the substrate reach-through, which is directly above the portion of the substrate reach-through previously formed, is also simultaneously formed along with the base. Then, emitter and collector reach-through regions are formed in the epitaxial layer followed by the step of providing electrical contacts. Deep dielectric isolation walls are formed at a suitable stage in the processing.