Image Number 2 for United States Patent #5557160.
A high resistance epitaxial layer is formed on a substrate, and a resistance layer is formed for each emitter by injecting ions into the high resistance epitaxial layer via an aperture formed through a gate electrode. An emitter is provided on the resistance layer. Alternatively, ions are injected into a semiconductor substrate of a first conductivity type to provide a region of a second conductivity type opposite to the first conductivity type in the semiconductor substrate by using a gate electrode having an aperture as a mask. An emitter is provided on the region of the semiconductor substrate.