Fast SCR structure for ESD protection

An ultra-low capacitance ESD protection device with an ultra-fast response time and a low turn-on voltage, and a high holding current. The device may include: a heavily-doped p-type substrate; a lightly-doped n-type epitaxial layer with a heavily-doped n-type buried layer; and a semiconductor-controlled rectifier (SCR) structure within the epitaxial layer. The SCR structure includes, between a ground terminal and a pad terminal: a shallow P+ region within a moderately-doped n-type well to form an emitter-base junction of a trigger transistor; a shallow N+ region within a moderately-doped p-type well to form an emitter-base junction of a latching transistor, and a PN junction coupled to either of the shallow regions as a forward-biased series diode. To reduce capacitance, the n-type and p-type wells are separated by a lightly-doped portion of the epitaxial layer having a small lateral dimension for enhanced switching speed.