| 摘要 |
After an oxide film has been completely removed from the surface of a substrate by dip etching, the substrate is inserted into a furnace at a temperature as low as about 400° C. to deposit an amorphous silicon film thereon with almost no oxide film existing therebetween. The amorphous silicon film is then patterned into a base electrode and a dopant contained in the base electrode is diffused into the substrate through annealing to form an extrinsic base diffused layer. Thereafter, an intrinsic base diffused layer is formed by ion implantation and an emitter diffused layer is formed by diffusing a dopant from an emitter electrode. Since an oxide film existing between the base electrode and the substrate can be thinner, excessive expansion of the extrinsic base diffused layer due to the diffusion of the dopant can be suppressed. As a result, a semiconductor device, including a bipolar transistor operating at a higher frequency with an increased emitter-base breakdown voltage and improved radio frequency characteristics, can be formed.
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