A method for producing a semiconductor device is disclosed. The method includes providing a semiconductor body having a first surface, and a second surface opposite the first surface, producing a first trench having a bottom and sidewalls and extending from the first surface into the semiconductor body, forming a dielectric layer along at least one sidewall of the trench, and filling the trench with a filling material. Forming the dielectric layer includes forming a protection layer on the least one sidewall such that the protection layer leaves a section of the at least one sidewall uncovered, oxidizing the semiconductor body in the region of the uncovered sidewall section to form a first section of the dielectric layer, removing the protection layer, and forming a second section of the dielectric layer on the at least one sidewall.