| 摘要 |
PURPOSE:To enable to control the breakdown voltage with a high accuracy by a method wherein a recess groove part is formed on the cathode side of the first conductivity type base layer, thereafter the second conductivity type base layer and emitter layer are formed, and further the first conductivity type emitter layer is so formed as to surround said groove part. CONSTITUTION:The junction J2 formed by a P type base layer 13 and an N-base layer 12 is well type having a curved part 18 by corresponding to the shape of a recess groove 17. A stepwise difference DELTAx between the part under said groove 17 of the junction J2 and the part positioned under an N-emitter layer 14 is equal to the depth Xoff of said groove 17. The VBO value for the generation of the over voltage trigger of VBO (breakdown voltage) free thyristor composed of such a structure is determined by the fifference DELTAx. In other word, since said difference DELTAx is determined only by the depth Xoff, the control of the value VBO becomes very easy, besides the controlling accuracy largely improves. |
