A process is described which permits the fabrication of very narrow base width bipolar transistors. The ability to selectively vary the transistor characteristics provides a degree of freedom for design of integrated circuits. The biplar transistor is processed up to the point of emitter formation using conventional techniques. But, prior to the emitter formation, a portion of the base area (22) wherein the emitter region (34) is planned to be formed is dry etched using reactive ion etching. The existing silicon nitride/silicon dioxide layers (24, 26) with the emitter opening (30) therein are used as the etching mask for this reactive ion etching procedure. Once the etching is completed to the desired depth, the normal processing is resumed to form the emitter and rest of the metallization. Since the intrinsic base under the emitter (34) is etched, and the normal emitter is formed afterwards, the etching reduces the base width by an amount approximately equal to the etched depth. The transistor characteristics depend strongly upon the base width so the etching is controlled to very tight dimensions.