This invention is generally concerned with power semiconductors such as
power MOS transistors, insulated gate by bipolar transistors (IGBTs),
high voltage diodes and the like, and method for their fabrication. A
power semiconductor, the semiconductor comprising a power device, said
power device having first and second electrical contact regions and a
drift region extending therebetween; and a semiconductor substrate
mounting said device; and wherein said power semiconductor includes an
electrically insulating layer between said semiconductor substrate and
said power device, said electrically insulating layer having a thickness
of at least 5 .mu.m.