Use of a camouflaged circuit

摘要

Connections between implanted regions (34a, 34b) in a semiconductor substrate (36), such as the sources (S1, S2) or drains (D1, D2) of adjacent transistors (T1, T2), are made by buried conductive implants (40) rather than upper level metalizations. The presence or absence of a connection between two implanted regions is camouflaged by implanting a conductive buried layer (40) of the same doping conductivity as the implanted regions when a connection is desired, and a field implant (44) of opposite conductivity to the implanted regions when no connection is desired, and forming steps (46a, 46b) into the substrate at the boundaries of the buried layer or field implant that mask the steps (52a, 52b) formed between different conductivity regions during a selective etch by a reverse engineer. The masking steps are preferably formed by field oxide layers (38) that terminate at the boundaries of the buried layers and field implants.