Complementary bipolar transistors having collector diffused isolation

Claim 1

A semiconductor device comprising: a first buried layer of a first conductivity type diffused into a substrate of a second conductivity type, a first region of said first conductivity type formed in a frame-like pattern overlapping the periphery of said first buried layer region, an epitaxial layer of said second conductivity type grown over said substrate, and said buried layer, a second region of said first conductivity type formed in a frame-like pattern in the surface of said epitaxial layer and aligned with said first region, said first and second regions being diffused toward each other through said grown epitaxial layer until said first and second regions overlap, a base region of said second conductivity type formed in the surface of said epitaxial region within said diffusion region and extending from the surface only part way through said epitaxial layer and being spaced at its bottom from said buried layer and an emitter region of said first conductivity type diffused into said base region, a second buried layer region of said first conductivity type in said substrate and spaced from said first buried layer, a third region of said first conductivity type in said second buried layer, said epitaxial layer being grown over said second buried layer, a fourth region of said first conductivity type in the surface of said grown epitaxial layer over said second buried layer region, said third and fourth regions diffused together to form a continuous base region of said first conductivity type extending from the surface of said grown epitaxial layer and down to said buried layer, an emitter region of said second conductivity type diffused into said base region at the surface of said grown epitaxial layer, and a collector region of said second conductivity type diffused into said base region at the surface of said grown epitaxial layer.