Abstract: A self-aligned process for the fabrication of a walled-emitter transistor includes the formation of an isolated device island on the surface of a semiconductor wafer. A layer of dielectric is then formed on the wafer, leaving only part of the device island exposed. A `substitute emitter` of silicon nitride is then formed on the exposed part of the device island in the position which will subsequently be occupied by the emitter. The exposed surface of the device island is then oxidized, some oxide being formed beneath the periphery of the substitute emitter. Oxide spacers are then formed non-lithographically about the periphery of the substitute emitter, after which the substitute emitter is removed and a base is formed in the semiconductor thus exposed. An emitter is then formed in the exposed semiconductor.