Abstract: An electrostatic discharge protection circuit that includes at least two transistors connected in a stacked configuration, a first diffusion region of a first dopant type shared by two adjacent transistors, and a second diffusion region of a second dopant type formed in the first diffusion region. A substrate-triggered site is induced into the device structure of the stacked transistors to improve ESD robustness and turn-on speed. An area-efficient layout to realize the stacked transistors is proposed. The stacked transistors may be implemented in ESD protection circuits with a mixed-voltage I/O interface, or in integrated circuits with multiple power supplies. The stacked transistors are fabricated without using a thick-gate mask.

Abstract: An ESD protection circuit with high substrate-triggering efficiency. The circuit comprises a multi-finger-type device having a plurality of finger gates below which a parasitic BJT is formed, a plurality of finger sources, each of which is an emitter of one parasitic BJT, and at least one finger drain coupled to a pad, a plurality of voltage drop elements, each of which is coupled between one of the finger sources and a power line to detect a transient current flowing through one of the finger gates, and a plurality of feedback circuits, each of which is coupled between a base and an emitter respectively of a first and second parasitic BJT, and activates the first BJT to bypass ESD current during an ESD event.