A silicon-carbide semiconductor substrate having a plurality of first doped regions being laterally spaced apart from one another and beneath a main surface, and a second doped region extending from the main surface to a third doped region that is above the first doped regions is formed. Fourth doped regions extending from the main surface to the first doped regions are formed. A gate trench having a bottom that is arranged over a portion of one of the first doped regions is formed. A high-temperature step is applied to the substrate so as to realign silicon-carbide atoms along sidewalls of the trench and form rounded corners in the gate trench. A surface layer that forms along the sidewalls of the gate trench during the high-temperature step from the substrate is removed.