Method of producing a semiconductor device

A method includes: forming a trench in a first major surface of a semiconductor substrate, the trench having a base and a side wall extending from the base to the first major surface; forming a first insulating layer on the trench base and side wall; forming a sacrificial layer on the first insulating layer on the trench side wall; forming a second insulation layer on the sacrificial layer; inserting conductive material into the trench that at least partially covers the second insulation layer; selectively removing portions of the second insulation layer uncovered by the conductive material; selectively removing the sacrificial layer to form a recess that is positioned adjacent the conductive material in the trench and that is bounded by the first insulation layer and the second insulating layer; and forming a third insulating layer in the trench that caps the recess to form an enclosed cavity in the trench.