A semiconductor device having a vertical drain extended MOS transistor may be formed by forming deep trench structures to define vertical drift regions of the transistor, so that each vertical drift region is bounded on at least two opposite sides by the deep trench structures. The deep trench structures are spaced so as to form RESURF regions for the drift region. Trench gates are formed in trenches in the substrate over the vertical drift regions. The body regions are located in the substrate over the vertical drift regions.