A method for forming a high voltage semiconductor power device comprises providing a first dopant source of first conductivity on an upper surface of a substrate of second conductivity. A second dopant source of first conductivity is provided on a lower surface of the substrate. The substrate is annealed for a first given time to drive the dopants from the first and second dopants sources into the substrate. The first and second dopant sources are removed from the upper and lower surfaces of the substrate. The substrate is annealed for a second given time to homogenize dopant concentration within the substrate after the first and second dopant sources have been removed, where the annealing the substrate for the second given time results in out-diffusion of dopants proximate the upper and lower surfaces of the substrate. Compensation dopants are provided into the substrate after annealing the substrate for the second given time to compensate the out-diffusion of the dopants proximate the upper and lower surfaces. The dopants driven into the substrate define an isolation diffusion structure that extends from the upper surface to the lower surface.