Overvoltage protection device

A circuit of protection against electrostatic discharges likely to occur on a first input/output terminal of a circuit to be protected, the protection circuit comprising, connected in series between said terminal and a reference terminal, the following:

• a first forward diode;
• a reverse diode having a punchthrough operation;
• a second forward diode;
• and
• a first diode with a reverse-controlled avalanche voltage.

A method of manufacturing a device of protection against electrostatic discharges, comprising:

• implanting, into a very heavily-doped semiconductor substrate of a first conductivity type, a first heavily-doped buried layer of a second conductivity type;
• implanting into the very heavily-doped semiconductor substrate a second heavily-doped buried layer of the first conductivity type;
• forming by epitaxy a first lightly-doped layer of the second conductivity type;
• forming a second heavily-doped layer of the first conductivity type, and
• performing a series of anneals causing diffusion of dopant atoms from the substrate through the first buried layer, to form a third layer of the first conductivity type between the first heavily-doped buried layer and the first lightly-doped layer.