Abstract of the Disclosure

An IC chip having a Zener diode with a subsurface breakdown junction to assure stable operation. The diode is formed by a triple diffusion process compatible with conventional bipolar processing. A deep p++ diffusion first is applied, reaching through the epitaxial region to buried n+ layer; next, a shallow p+ diffusion is formed over the deep p++ diffusion and extending laterally beyond that diffusion; finally, a shallow n+ diffusion is applied over the p diffusions, to form a subsurface breakdown junction therewith. The topology of the mask windows is selected to provide concentration profiles which insure that the breakdown occurs at the subsurface junction, and that other desirable diode characteristics are achieved

• a cross-section view of an IC diode fabricated in accordance with this invention.

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