Low saturation resistance,low offset voltage,monolithic analog switch

Claim 1

A monolithic semiconductor device structure capable of operation as an analog switch with low saturation resistance and very low offset voltage in the on state and high impedance in the off state comprising a first conductivity type substrate; a second conductivity type epitaxial layer on said substrate; a buried layer region of the second conductivity type selectively positioned between said epitaxial layer and said substrate; and isolation diffusion of said first conductivity type extending from the upper surface of said epitaxial layer through said epitaxial layer, contacting said substrate and completely surrounding and isolating said epitaxial layer from other portions of said substrate; a plurality of annular second conductivity type wall regions within said isolation diffusions extending from the upper surface of said buried layer region so as to form a plurality of tubs of second conductivity type epitaxial material, said buried layer region and said wall regions having a higher conductivity then said epitaxial material; a first conductivity type base region diffused within each of said tubs defining the base of the transistor and a second conductivity type emitter regions substantially filling said base regions except for portions surrounding areas of the base region which extend to the surfAce, said emitter region having a higher conductivity then said buried layer and said epitaxial material; said base material which extends to the surface and surrounded by said emitter region serving as the base contact for the device whereby said device has an offset voltage of less then one hundredth of a volt and an inverse saturation resistance of less then 5 ohms.