The present disclosure provides a bipolar junction transistor (BJT) device and methods for manufacturing the BJT device. In an embodiment, the BJT device includes: a semiconductor substrate having a collector region, and a material layer disposed over the semiconductor layer. The material layer has a trench therein that exposes a portion of the collector region. A base structure, spacers, and emitter structure are disposed within the trench of the material layer. Each spacer has a top width and a bottom width, the top width being substantially equal to the bottom width.