SEMICONDUCTOR DEVICE AND METHOD OF FABRICATING AN ELECTRICALLY INSULATING STRUCTURE IN A TRENCH

In an exemplary embodiment, a semiconductor device includes: a semiconductor substrate having a first major surface; a trench positioned in the semiconductor substrate and having a width, a base, and a side wall extending from the base to the first major surface; a first electrically insulating layer that lines the base and the side wall of the trench; and an electrically insulating plug that is positioned in the trench and that extends across the entire width of the trench. The plug has a lower surface that forms an interface with the first electrically insulating layer and an upper surface. The upper surface of the plug is coplanar with the first major surface of the semiconductor substrate or positioned within the trench.