Wafer trench article and process

This invention relates generally to semiconductor wafer processing and, in particular, to processes that form trenches in wafers while reducing device stress and defects. A bonded wafer has a device substrate with isolation trenches defining device regions Oxide dogbone structures are removed before filling trenches . Voids in the trenches are spaced from the top of the trenches. The trenches are covered with an oxide layer and filled with polysilicon A LOCOS mask structure comprising a layer of CVD pad oxide and silicon nitride cover the trenches and the adjacent device substrate regions.