A WSi2/polycrystalline silicon/Si bulk system has been studied in the framework of a complementary metal‐oxide‐semiconductor compatible self‐aligned bipolar transistor technology. The WSi2silicide is implanted with As and used as a dopant source for the formation of the polycrystalline silicon‐bulk emitter. The effect of the polycrystalline silicon/monocrystalline silicon interface has been investigated, as well as the reproducibility of the process for the emitter formation. The role of boron on the arsenic diffusion process has been analyzed, with boron being implanted (a) in the silicon bulk for the intrinsic base formation, and (b) in the WSi2silicide at the extrinsic base implantation step in the self‐aligned process. Experimental results give dopant diffusion and segregation coefficients and are used to adjust the parameters of our process simulation program on the technological process.