A semiconductor device has a vertical drain extended MOS transistor with deep trench structures to define a vertical drift region and at least one vertical drain contact region, separated from the vertical drift region by at least one instance of the deep trench structures. Dopants are implanted into the vertical drain contact regions and the semiconductor device is annealed so that the implanted dopants diffuse proximate to a bottom of the deep trench structures. The vertical drain contact regions make electrical contact to the proximate vertical drift region at the bottom of the intervening deep trench structure. At least one gate, body region and source region are formed above the drift region at, or proximate to, a top surface of a substrate of the semiconductor device. The deep trench structures are spaced so as to form RESURF regions for the drift region.