Method for Forming a Power Semiconductor Device and a Power Semiconductor Device

A method of forming a power semiconductor device includes providing a semiconductor layer of a first conductivity type extending to a first side and having a first doping concentration of first dopants providing majority charge carriers of a first electric charge type in the layer, and forming a deep trench isolation including forming a trench which extends from the first side into the semiconductor layer and includes, in a vertical cross-section perpendicular to the first side, a wall, forming a compensation semiconductor region of the first conductivity type at the wall and having a second doping concentration of the first dopants higher than the first doping concentration, and filling the trench with a dielectric material. The amount of first dopants in the compensation semiconductor region is such that a field-effect of fixed charges of the first electric charge type which are trapped in the trench is at least partly compensated.