A zener diode capable of breakdown at much higher voltages than in the prior art is fabricated by providing a semiconductor substrate of a first conductivity type having an opposite conductivity type first tank disposed therein. The first tank includes relatively lower and relatively higher resistivity portions, the relatively lower doped portion isolating the relatively higher doped portion from the substrate. A first region of first conductivity type is disposed in the higher doped portion and a second region of opposite conductivity type and more highly doped than the first tank is spaced from the first region. Structure is provided between the first and second regions for repelling majority charge carriers associated with the opposite conductivity type which can be a field plate spaced from the first tank; a portion at the surface of the first tank having the first conductivity type; or a tank, of first conductivity type disposed in the first tank, abutting the first region, extending more deeply into the first tank than does the first region and more lightly doped than the first region. In accordance with a further embodiment, the diode includes a semiconductor substrate, a first tank portion disposed in the substrate and a second tank portion disposed in the first tank portion as in the prior embodiments. A first region of first conductivity type is disposed in the second tank portion and extends into the first tank portion. A second region of opposite conductivity type more highly doped than the first tank portion is disposed in the first tank portion and spaced from the first region.