with a non doped epitaxy where the maximum and minimum values fluctuate about twice as much concentration fluctuations are noticeably minimized owing to the homogeneous pre doping of the epitaxial layers in the range of 20 to 80 atomic the homogeneously distributed proportion of doping material in the epitaxial growth phases can be limited to a third of the total concentration of doping material for the first conduction type while two thirds subsequently have to be introduced near the surface by ion implantation in this embodiment of the invention it is on the other hand desirable that the proportion of doping material introduced by ion implantation is significantly larger than the proportion introduced into the semiconductor crystal by homogeneous doping in the epitaxial growth phase fluctuations in the concentration of doping material for the drift zones can be reduced further by using a technology and a manufacturing process described below with reference to fig1 to 18 and resulting in a semiconductor device illustrated in fig1 this method is likewise based on a semiconductor wafer 16 as illustrated in fig1 which is highly doped with an n type doping material fig1 illustrates a diagrammatic cross section through the semiconductor wafer 16 according to fig1 following the completion of a first epitaxial growth phase in this epitaxial growth phase however the doping material is not introduced homogeneously but rather inhomogeneously i e the addition of doping material is reduced or stopped completely during the epitaxial growth process resulting in a maximum of doping material approximately in the middle of the epitaxial growth phase the boundaries of the region with a maximum doping n max are indicated by dot dash lines in the epitaxial layer 18 of fig1.