Patent ID: 8450793

Claim:
A controlled-punch-through semiconductor device comprising: a four-layer structure having a collector on a collector side and an emitter on an emitter side which lies opposite the collector side; a base layer between the emitter and the collector; a first buffer layer, which lies on the collector side between the base layer and the collector, the first buffer layer having in a first depth from the collector a first peak doping concentration, which is higher than the base layer; a second buffer layer, which lies between the first buffer layer and the base layer, the second buffer layer having in a second depth from the collector a second peak doping concentration which is lower than the first peak doping concentration of the first buffer layer; and a third buffer layer arranged between the second depth and the first depth with a doping concentration which is higher than the doping of the base layer and which is lower than the second peak doping concentration of the second buffer layer.