Integrated Circuit and Method of Forming an Integrated Circuit

A semiconductor device, comprising:

• a semiconductor body comprising a main surface and a rear surface opposite the main surface;
• and
• a trench that extends from the main surface of the semiconductor body towards the rear surface, the trench comprising an upper trench portion and a lower trench portion, the trench having a width measured along a plane parallel to the main surface;
• wherein:
• the upper trench portion comprises curved sidewalls that that bow outward from a bottom of the upper trench portion;
• the lower trench portion comprises generally planar sidewalls that extend from bottom of the upper trench portion at a first depth into the semiconductor body along the first direction to a contact region at a second depth, the lower trench portion being narrower than the widened part of the upper trench portion;
• an insulation layer lining the curved sidewalls of the upper trench portion and the generally planar sidewalls of the lower trench portion, wherein the insulation layer has an opening at the bottom of the trench;
• and
• an electrically conductive contact electrode within the trench, wherein the contact electrode is electrically connected to the semiconductor body at the bottom of the trench and electrically insulated from the semiconductor body along the curved sidewalls and the generally planar sidewalls by the insulation layer.