US Patent 8669640 Bipolar transistor

An improved device (20) is provided, comprising, merged vertical (251) and lateral transistors (252), comprising thin collector regions (34) of a first conductivity type sandwiched between upper (362) and lower (30) base regions of opposite conductivity type that are Ohmically coupled via intermediate regions (32, 361) of the same conductivity type and to the base contact (38). The emitter (40) is provided in the upper base region (362) and the collector contact (42) is provided in outlying sinker regions (28) extending to the thin collector regions (34) and an underlying buried layer (28). As the collector voltage increases part of the thin collector regions (34) become depleted of carriers from the top by the upper (362) and from the bottom by the lower (30) base regions. This clamps the thin collector regions' (34) voltage well below the breakdown voltage of the PN junction formed between the buried layer (28) and the lower base region (30). The gain and Early Voltage are increased and decoupled and a higher breakdown voltage is obtained.