A trench etch mask is formed on a process surface of a semiconductor layer. By using the trench etch mask, both first trenches and second trenches are formed that extend from the process surface into the semiconductor layer. The first and second trenches alternate along at least one horizontal direction parallel to the process surface. First semiconductor regions of a first conductivity type are formed in the first trenches. Second semiconductor regions of a second, opposite conductivity type are formed in the second trenches.