A vertical semiconductor device includes a semiconductor body, and first and second contacts on opposite sides of the semiconductor body. A plurality of regions are formed in the semiconductor body including, in a direction from the first contact to the second contact, a first region of a first conductivity type, a second region of a second conductivity type; and a third region of the first conductivity type. The third region is electrically connected to the second contact. A semiconductor zone of the second conductivity type and increased doping density is arranged in the second region. The semiconductor zone separates a first part of the second region from a second part of the second region. The semiconductor zone has a maximum doping density exceeding about 1016 cm−3 and a thickness along the direction from the first contact to the second contact of less than about 3 μm.