Methods to control the threshold voltage of a deep trench corner device

1. Field of the Invention A method of manufacturing a semiconductor trench device comprises forming a dielectric on a substrate, the dielectric having an underlying oxide layer adjacent the substrate, etching a trench in the dielectric and the substrate, forming a recess in the underlying oxide layer, filling the recess with a nitride plug, filling the trench a conductive material and oxidizing the dielectric and the conductive material, wherein the nitride plug controls a shape of a corner of the trench.