Semiconductor module

Method for producing a controlled-punch-through semiconductor device having a four-layer structure with layers of different conductivity types, and having a collector on a collector side and an emitter on an emitter side which lies opposite the collector side, the method comprising:

• producing layers on the emitter side of a wafer of a first conductivity type;
• thinning the wafer on a second side opposite the emitter side subsequent to the producing of layers;
• applying particles of the first conductivity type to the wafer on the second side, which particles form a first buffer layer in the semiconductor device, the first buffer layer having a first peak doping concentration in a first depth, which first peak doping concentration is higher than a doping of the wafer;
• applying particles of a second conductivity type to the wafer on the second side, which particles form a collector layer on the collector side of the semiconductor device;
• forming a collector metallization on the second side after applying the particles of the first and second conductivity types;
• applying, at any stage of the method, particles of the first conductivity type to the wafer on the second side by implantation of the particles, which particles form a second buffer layer in the semiconductor device, the second buffer layer having in a second depth, which second depth is greater than the first depth, a second peak doping concentration, which is lower than the first peak doping concentration of the first buffer layer and which is higher than the doping of the wafer, the first and second buffer layers being formed such that a third buffer layer is created between the second depth and the first depth with a doping concentration which is higher than the doping of the wafer and which is lower than the second peak doping concentration of the second buffer layer;
• and
• performing at least one wafer thermal treatment for forming at least one of the first buffer layer, the second buffer layer and the collector layer in the semiconductor device at any stage after applying the particles for at least one of the first buffer layer, the second buffer layer and the collector layer to the wafer.