Semiconductor Device with Auxiliary Structure Including Deep Level Dopants

An insulated gate bipolar transistor comprising:

• transistor cells formed along a first surface at a front side of a semiconductor body in a transistor cell area;
• a drift zone structure forming first pn junctions with body zones of the transistor cells;
• an auxiliary structure between the drift zone structure and a second surface at a rear side of the semiconductor body, wherein at least a first portion of the auxiliary structure contains deep level dopants requiring at least 150 meV to ionize;
• and
• a collector structure directly adjoining the auxiliary structure, wherein an injection efficiency of minority carriers from the collector structure into the drift zone structure varies along a direction parallel to the first surface at least in the transistor cell area.