Importance

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Abstract

A circuit protects against electrostatic discharge and includes a pad which receives an external signal source. The transistor of the present invention is connected to the circuit to be protected and includes a semiconductor body of a first conductivity type and serves as the collector of the transistor and is connected to the pad. A first doped region of a second conductivity type is contained in the semiconductor body and serves as the base of the transistor and forms a collector-to-base junction surface with the semiconductor body. A second doped region of the first conductivity type is contained in the first doped region and serves as the emitter of the transistor and forms a base-to-emitter junction surface with the first doped region. The first and second doped regions are electrically connected for establishing a shorted connection between the base and emitter. The first doped region includes a generally H-shaped doped region and a generally ring-shaped doped region forming an opening in which the second doped region serving as the emitter is received. The H-shaped doped region has a deeper junction surface than the junction surface of the ring-shaped doped region, and a dopant concentration that is less than the dopant concentration of the ring-shaped doped region. The H-shaped doped region achieves a low collector-to-base breakdown voltage and the ring-shaped doped region achieves a low snap-back voltage. A method for forming the transistor is also disclosed.

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First Claim