Abstract: The present invention relates to a circuit device for protection against electrostatic discharge, and being immune to the latch-up phenomenon. The circuit device is of the integrated type in a portion of a semiconductor integrated circuit. The device includes an active limiting element and a resistor connected in series between a terminal of the active element connected to an input/output pin of the integrated circuit, and a terminal of a circuit to be protected. The active element is a bipolar transistor having a base terminal and an emitter-acting collector terminal connected together. The distributed resistor is formed in an emitter-acting collector region of the transistor which is diffused and elongated at the surface inside a base pocket of the transistor.

Abstract: The device has an SCR structure in a P surface zone of a silicon die. A P+ anode region for connection to an I/O terminal to be protected is formed in an N region, as well as an N+ contact region; an N+ cathode region is formed in another N region for connection to the earth of the integrated circuit. The striking potential of the SCR, that is, the intervention potential of the protection device, is determined by the reverse breakdown of the junction between the first N region and the P-body surface zone. This potential is influenced by an electrode which is disposed over the junction and is connected to the cathode constituting the gate of a cut-off N-channel MOS transistor. The concentrations are selected in a manner such that the P-channel MOS transistor defined by the P region, by the portion of the first region over which the electrode is disposed, and by the P-body, has a conduction threshold greater than the striking potential.