A semiconductor device includes a semiconductor region having charge carriers of a first conductivity type, a transistor cell in the semiconductor region, and a semiconductor channel region in the transistor cell and having a first doping concentration of charge carriers of a second conductivity type. A semiconductor auxiliary region in the semiconductor region has a second doping concentration of charge carriers of the second conductivity type, which is at least 30% higher than the first doping concentration. A pn-junction between the semiconductor auxiliary region and the semiconductor region is positioned as deep or deeper in the semiconductor region as a pn-junction between the semiconductor channel region and the semiconductor region. The semiconductor auxiliary region is positioned closer to the semiconductor channel region than any other semiconductor region having charge carriers of the second conductivity type and that forms a further pn-junction with the semiconductor region.