A method of forming a silicon-germanium heterojunction bipolar transistor (hbt) device is provided. The method includes forming a stack of four doped semiconductor layers on a semiconductor substrate. The method further includes forming a dummy emitter contact and contact spacers on a fourth doped semiconductor layer of the stack of four doped semiconductor layers, and removing portions of the second, third, and fourth semiconductor layers to form a vertical fin. The method further includes recessing the second and fourth doped semiconductor layers, and depositing a condensation layer on the second, third, and fourth doped semiconductor layers. The method further includes reacting the condensation layer with the third doped semiconductor layer to form a protective segment on a condensed protruding portion.