A bipolar non-punch-through power semiconductor device comprising a semiconductor wafer and a first electrode on a first main side of the wafer and a second electrode on a second main side of the wafer opposite the first main side, the semiconductor wafer comprising at least a two-layer structure with layers of different conductivity types, the at least two-layer structure comprising - a drift layer of a first conductivity type, and - a first layer of a second conductivity type, which is different from the first conductivity type, wherein the first layer is arranged on the drift layer towards the first main side and contacts the first electrode, and the semiconductor wafer further comprising - an inner region having a thickness measured between the first and second main side and an outer region, which surrounds the inner region, having a maximum thickness, which is the maximum thickness, measured between the first and second main side of the outer region, wherein the maximum thickness is greater on the first main side of the outer region than the thickness on the first main side of the inner region, - wherein the drift layer has a thickness in the inner region being greater than or equal to a thickness of the drift layer in the outer region, - wherein the first layer has a first section in the inner region and a second section in the outer region, and - wherein a thickness of the first layer increases in a transition region between the inner region and the outer region from a thickness of the first section of the first layer in the inner region to a maximum thickness of the second section of the first layer in the outer region, characterized in, that - the thickness of the first layer increases linearly over the transition region with a width of the transition region being greater than 5 times the thickness of the first section of the first layer, preferably 10 to 20 times the thickness of the first section of the first layer. - a drift layer of a first conductivity type, and - a first layer of a second conductivity type, which is different from the first conductivity type, wherein the first layer is arranged on the drift layer towards the first main side and contacts the first electrode, and the semiconductor wafer further comprising - an inner region having a thickness measured between the first and second main side and an outer region, which surrounds the inner region, having a maximum thickness, which is the maximum thickness, measured between the first and second main side of the outer region, wherein the maximum thickness is greater on the first main side of the outer region than the thickness on the first main side of the inner region, - wherein the drift layer has a thickness in the inner region being greater than or equal to a thickness of the drift layer in the outer region, - wherein the first layer has a first section in the inner region and a second section in the outer region, and - wherein a thickness of the first layer increases in a transition region between the inner region and the outer region from a thickness of the first section of the first layer in the inner region to a maximum thickness of the second section of the first layer in the outer region, characterized in, that - the thickness of the first layer increases linearly over the transition region with a width of the transition region being greater than 5 times the thickness of the first section of the first layer, preferably 10 to 20 times the thickness of the first section of the first layer.