| 摘要 |
PURPOSE:To secure specified protective overvoltage value by a method wherein, when an N type base layer with its surface projecting flatly is formed in a P type emitter substrate and the periphery is encircled by an N type emitter layer to make a thyristor, multiple floating concentric circular P type regions are provided on the flat part of base layer. CONSTITUTION:An N type base layer 12 with its central part projecting roundly and flatly is provided in a P type emitter layer 11 with an anode electrode 21 provided on backside to be encircled by a P type base layer 13 and then an N type emitter layer 14 encircling the layer 12 is formed on the base layer 13. Next a gate electrode 31 is mounted on the space between the base layer 12 and the emitter layer 14 while the emitter layer 14 is coated with a circular cathode electrode 22. Later a groove 18 for improving withstand voltage entering into the base layer 12 is cut outside the electrode 22 while multiple circular field limiting rings 15 are excavated in the round and flat part of base layer 12 to improve the withstand voltage of major junctions 16 impressed with overvoltage at the ends of round and flat part. |
