A unipolar semiconductor device having a drift layer (3) doped according to a first conductivity type forming a conducting path and regions (7, 8) doped according to a second conductivity type and arranged next to the drift layer, has the drift layer and the regions of a semiconductor material having an ionization energy Ei of dopants of the second conductivity type therein exceeding 0.5 eV and/or a solubility of the dopants of the second conductivity type therein being less than 1018 cm−3.