A controlled-punch-through semiconductor device with a four-layer structure is disclosed which includes layers of different conductivity types, a collector on a collector side, and an emitter on an emitter side which lies opposite the collector side. The semiconductor device can be produced by a method performed in the following order: producing layers on the emitter side of wafer of a first conductivity type; thinning the wafer on a second side; applying particles of the first conductivity type to the wafer on the collector side for forming a first buffer layer having a first peak doping concentration in a first depth, which is higher than doping of the wafer; applying particles of a second conductivity type to the wafer on the second side for forming a collector layer on the collector side; and forming a collector metallization on the second side. At any stage particles of the first conductivity type can be applied to the wafer on the second side for forming a second buffer layer with a second peak doping concentration lower than the first peak doping concentration of the first buffer layer, but higher than the doping of the wafer. A third buffer layer can be arranged between the first depth and the second depth with a doping concentration which is lower than the second peak doping concentration of the second buffer layer. Thermal treatment can be used for forming the first buffer layer, the second buffer layer and/or the collector layer.