Consistent with an example embodiment, a reduced surface field effect type (RESURF) semiconductor device is manufactured having a drift region over a drain region. Trenches are formed through openings in mask. A trench insulating layer is deposited on the sidewalls and base of the trenches followed by an overetching step to remove the trench insulating layer from the base of the trenches as well as the top of the sidewalls of the trenches adjacent to the first major surface leaving exposed silicon at the top of the sidewalls of the trench and the base of the trenches. Silicon is selectively grown plugging the trenches with silicon plug (18) leaving void.