Semiconductor oxide pillars are selectively grown on semiconductor mesas between precursor structures that extend from a main surface into a semiconductor substrate. Spaces between the semiconductor oxide pillars are filled with one or more auxiliary materials to form alignment plugs in a vertical projection of the precursor structures. The semiconductor oxide pillars are removed selectively against the alignment plugs. Contact spacers are provided along sidewalls of the alignment plugs. Between opposing ones of the contact spacers contact plugs are provided directly adjoining the semiconductor mesas. The contact plugs are self-aligned to the semiconductor mesas and allow a further reduction of the lateral dimensions of the semiconductor mesas without recessing the semiconductor mesas.