The optimization of base width and base doping of punch-through (PT) junction used in bipolar and unipolar high voltage power devices is analyzed in this paper. From analysis of a normalized form, the difference of the optimization design of PT junction between the bipolar and unipolar high voltage power devices is evaluated, and then a set of expressions of optimum base width and base doping for such both high voltage power devices are presented. (C) 2002 Elsevier Science Ltd. All rights reserved.