A semiconductor device includes a semiconductor body including a trench with first and second opposing sidewalls. A first electrode is arranged in a lower portion of the trench and a second electrode in an upper portion of the trench. A dielectric structure is arranged in the trench, including a first portion between the electrodes. The first portion includes, in sequence along a lateral direction from the first sidewall to the second sidewall, a first part including a first dielectric material, a second part including a second dielectric material selectively etchable to the first dielectric material, a third part including the first dielectric material, the first dielectric material of the third part being continuously arranged along a vertical direction from a top side of the first electrode to a bottom side of the second electrode, a fourth part including the second dielectric material and a fifth part including the first dielectric material.