In making a vertical bipolar transistors, after forming by diffusion process a region to become inactive base region an oxide film is selectively formed on the region, thereafter an ion implantation is carried out to produce regions which become the active base region and emitter region by using the oxide film; thereby such a configuration is formed so that defect part (108) induced at the time of the ion implantation is confined in the emitter region, thereby minimizing the leakage current at the PN junction, and hence assuring production of high performance and high reliability semiconductor devices; further, a high integration is attained by adopting self-alignment in forming emitter contact.