FIG. 7 further illustrates the drift region 153 which includes an upper drift region 153a and a surface doping region 155 which is formed at the first side 101 of the semiconductor substrate 100. The surface doping region 155 laterally completely extend from the outer end of the active area 104 to the lateral rim 103 of the semiconductor substrate 100. According to an embodiment, the surface doping region 155 is only formed in an outer part of the edge termination area 110 extending to the lateral rim 103 while the upper drift region 153a is formed to extend to the first side 101 in an inner part of the edge termination area 110 next to the active area 104.

In addition to improving the avalanche breakdown robustness of the edge termination area, the surface doping region 155 with reduced net doping concentration also helps to reduce the electric field at the lateral end of the body region, where the electric field can also be critical.

A further improvement for the electrical field relaxation in the edge termination area 110 is to place a so-called source runner and/or a so-called gate runner above the critical region at the end of the edge termination area. Each of these runners are at comparably low voltage or at 0 V during blocking mode. These electrical structures push the electrical field lines further away from the most outer trench leading to a further reduction of the electrical field strength. Embodiments with gate runners and source runners are illustrated in FIGS. 8A and 8B.