A model for the lateral junction contour of double-diffused Gaussian profiles

A general closed-form expression is obtained for the lateral junction contour of double-diffused Gaussian profiles which is applicable for process and device modeling. The channel-source junction contour of self-aligned double-diffused Gaussian MOS (DMOS) transistor structures, in which both diffusions have the same oxide mask edge, is found to be a quarter-circle with the origin displaced toward the interior of the oxide mask openings. The junction contour of double-diffused Gaussian bipolar transistor structures, where emitter and base regions have different mask openings, closely approximates an ellipse.