The present application provides methods for manufacturing BiCMOS device and the heterojunction bipolar transistor (HBT) contained therein. In formation of a raised extrinsic base region of the heterojunction bipolar transistor, the epitaxial silicon is doped with carbon (C) and boron (B) in situ and is doped with a metal catalyst simultaneously, then, the plasma treatment and the laser annealing are conducted to the carbon, and a graphene region is formed in the Si epitaxial layer. Because of high conductivity of graphene, the base resistance of the SiGe HBT can be reduced to enhance its radiation performance. The above method can be applied to conventional BiCMOS device process by performing plasma treatment and laser annealing to the doped carbon to form the graphene region in the extrinsic base region. The method is easily controlled and integrated into conventional BiCMOS device process.