A technique for making a bulk isolated PN diode is disclosed. In one embodiment, a method may include providing a substrate having a doped region and disposing a dielectric material over the doped region. The method may also include forming first and second holes in the dielectric material exposing the doped region, and forming respective first and second polysilicon plugs within the first and second holes over the doped region. In one embodiment, the first and second polysilicon plugs are doped opposite one another such that a PN junction is formed between the first or second polysilicon plug and the doped region of the substrate, and has a cross-sectional area generally defined by the first or second hole adjacent the PN junction. Various devices, systems, and other methods are also disclosed.