The present disclosure provides embodiments of bipolar junction transistor (BJT) structures. A BJT according to the present disclosure includes a first epitaxial feature disposed over a well region, a second epitaxial feature disposed over the well region, a vertical stack of channel members each extending lengthwise between the first epitaxial feature and the second epitaxial feature, a gate structure wrapping around each of the vertical stack of channel members, a first electrode coupled to the well region, an emitter electrode disposed over and coupled to the first epitaxial feature, and a second electrode disposed over and coupled to the second epitaxial feature.