A reverse-conducting semiconductor device is disclosed with an electrically active region, which includes a freewheeling diode and an insulated gate bipolar transistor on a common wafer. Part of the wafer forms a base layer with a base layer thickness. A first layer of a first conductivity type with at least one first region and a second layer of a second conductivity type with at least one second and third region are alternately arranged on the collector side. Each region has a region area with a region width surrounded by a region border. The RC-IGBT can be configured such that the following exemplary geometrical rules are fulfilled: each third region area is an area, in which any two first regions have a distance bigger (i.e., larger) than two times the base layer thickness; the at least one second region is that part of the second layer, which is not the at least one third region; the at least one third region is arranged in the central part of the active region in such a way that there is a minimum distance between the third region border to the active region border of at least once the base layer thickness; the sum of the areas of the at least one third region is between 10 and 30% of the active region; and each first region width is smaller than the base layer thickness.