In one aspect, a diode includes a substrate having a first type dopant; a buried layer having a second type dopant and formed within the substrate; an epitaxial layer having the second type dopant and formed above the buried layer; and a plurality of regions having the first type dopant within the epitaxial layer. The plurality of regions includes a first region, a second region, and a third region. The diode also includes a base well having the first type dopant and located within the epitaxial layer and in contact with the third and fourth regions. In a reverse-bias mode, the diode is an electrostatic discharge (ESD) clamp and forms parasitic transistors comprising a first bipolar junction transistor (BJT), a second BJT and a third BJT.