Semiconductor device and process for its preparation

A thin semiconductor wafer 101 on which a surface structure 133 and a lower surface structure 134 are formed, resulting the semiconductor chip is fixed by means of a double-sided adhesive tape 137 on a carrier substrate 141st Then, on the thin semiconductor substrate 101 by wet anisotropic etching of a trench to be a score line is formed so that a crystal face is exposed as a side wall of the trench. On this side wall of the trench with the exposed crystal face of an insulating separating layer 145 is formed to withstand a voltage applied in the backward direction voltage up to the breakdown voltage by ion implantation and a heat treatment at moderate temperature or a laser heat treatment so that on the one hand, extends up to the upper side surface, while on the other hand is in contact with a p-type collector region 110, which forms a lower-side diffused layer. A laser dicing is performed so that a collector electrode 111, which sits on the p-type collector region 110, is cut clean along with the p-type collector region 110, without any projecting parts or missing parts formed under the release layer 145th Subsequently, the double-sided adhesive tape 137 is peeled from the collector electrode 111, whereby the thin semiconductor wafer 101 becomes a semiconductor chip. This process produces highly reliable, backward ...