Embodiments of the disclosure provide a bipolar junction transistor (BJT) structure and related method. A BJT according to the disclosure may include a base over a semiconductor substrate. A collector is over the semiconductor substrate and laterally abuts a first horizontal end of the base. An emitter is over the semiconductor substrate and laterally abuts a second horizontal end of the base opposite the first horizontal end. A horizontal interface between the emitter and the base is smaller than a horizontal interface between the collector and the base.