Abstract of the Disclosure

Describes a structure for and method of making ohmic contact to a buried, highly conductive layer in a dielectrically isolated semiconductor pocket in order to eliminate potential failure modes and reduce signal-path resistance in the lower region of the pocket. Essentially, a raised area is formed adjacent to but separated from a side of the semiconductor pocket, the raised area comprising a portion of the buried, highly conductive layer to which contact is made from the pocket upper surface. The invention is particularly suitable for fabricating composite semiconductor devices, such as integrated circuits or arrays, in which complex integrated arrays of semiconductor elements are electrically isolated from each other and all are formed within a single unitary structure.

• Figure 1 is a simplified, cross-sectional view of a prior art device showing a dielectrically isolated semiconductor pocket in which contact is made to the highly conductive underlayer at the edge of the pocket via a highly conductive contact region extending from the surface of the pocket itself.
• Figure 2 is a simplified cross-sectional view of a portion of a prior art device showing a possible failure mode, resulting from misalignment of the contact region.
• Figure 3 is a simplified cross-sectional view of a portion of a prior art device showing a possible failure mode, resulting from a miscalculation during the semiconductor removal step.
• Figure 4 is a simplified cross-sectional view of one pocket of the preferred embodiment of the invention showing contact to a raised portion of the highly conductive underlayer at a place separated from the edge of the pocket.

 Citations [54]:
  
3,381,182  04/1968  Thorton
3,412,295  11/1968  Grebene