Semiconductor device having electrically insulating barriers for surface leakage sensitive devices and method of forming

Claim 1

A semiconductor device comprising: a heavily doped semiconductor substrate; a lightly doped epitaxial layer overlying a surface of said substrate and having the same conductivity type as said substrate; an electrically insulating layer disposed on the surface of said epitaxial layer at selected locations and comprising a separate portion at each location; said epitaxial layer having a surface leakage sensitive device therein beneath each separated portion of said insulating layer; a plurality of electrically insulating barriers extending from the surface of said epitaxial layer through said epitaxial layer and into said substrate to electrically isolate surface leakage sensitive areas of said devices from each other; said insulating barriers having a depth greater than the depth of said insulating layer, the depth of said insulating barriers being at least as great as that of said epitaxial layer; a highly doped diffusion of opposite conductivity type to said substrate and said epitaxial layer disposed in said epitaxial layer and in contact with said insulating barriers; each of said insulating barriers extending into said substrate for a distance less than the thickness of said substrate and laterally surrounding each said surface leakage sensitive device except where each said barrier is discontinuous to allow a conductive path between said diffusion and a respective one of said surface leakage sensitive devices; said conductive path comprising the entire thickness of said epitaxial layer said diffusion and each of said surface leakage sensitive devices being located on opposite sides of said discontinuous barriers; and each said conductive path constituting a component part of a respective one of said surface leakage sensitive devices.