A bipolar junction transistor includes an emitter region, a base region, a collector region and an isolation structure. The base region is disposed adjacent to a first side of the emitter region. The collector region is disposed adjacent to a second side of the emitter region. The isolation structure is disposed between the emitter region and each of the base region and the collector region.

A semiconductor device includes a base region having a first conductivity type, the base region extending into a top surface of a semiconductor layer, a collector region having an opposite second conductivity type, the collector region extending from the top surface into the semiconductor layer and spaced apart from the base region, and an emitter region having the second conductivity type, the emitter region extending from the top surface into the base region and having first and second faces along a junction between the emitter region and the base region.