Patent ID: 6864542

Claim:
A bipolar PNP transistor formed in two successive epitaxial layers on a P-type substrate, including: in a central portion of the PNP bipolar transistor a first N area diffused in the P-type substrate, a second P + area formed in a first epitaxial layer of the two successive epitaxial layers, an N base and P + emitter structure formed in a second epitaxial layer of the two successive epitaxial layers; a first ring-shaped trench crossing the two successive epitaxial layers and penetrating into the P-type substrate, the second P + area being laterally delimited by the first ring-shaped trench, the first N area extending at least partially under the first ring-shaped trench; and outside the first ring-shaped trench, a third N + area formed in the first epitaxial layer and contacting the first N area.