Ruggedized symmetrically bidirectional bipolar power transistor

A semiconductor device, comprising, on BOTH surfaces of a first-conductivity-type semiconductor die:

• a second-conductivity-type emitter/collector region, surrounded by a first insulated trench having a conductive electrode therein;
• and
• a first-conductivity-type base contact region, laterally separated from the emitter/collector region by the first insulated trench, and making ohmic contact to the bulk of the semiconductor die;
• wherein an interior of the emitter/collector region includes, at locations at a distance from sides of the surrounding first insulated trench and separated from the first insulated trench and not at locations adjacent to and not contacting the first insulated trench, and at a distance from and not overlapping or contacting a vertical plane of said sides of the surrounding first insulated trench, breakdown initiation regions where an additional implanted population of second-conductivity-type dopant atoms causes creates embedded enriched regions of second-conductivity-type dopant, compared to the adjacent region of second-conductivity-type of the second-conductivity-type emitter/collector region, said enriched regions exhibiting a reduced breakdown voltage;
• whereby breakdown, under overvoltage conditions, begins near the initiation regions, and thereby minimizes hot carrier injection into the first insulated trench.