| 摘要 |
PROBLEM TO BE SOLVED: To form bipolar elements having different characteristics depending on different shapes of base layers on the same substrate simultaneously in a common process. SOLUTION: A semiconductor substrate 210 has an epitaxial layer 240 which is taper-etched to form a horizontal part 240A and a slope 240B. A base layer 270 of a usual transistor is provided on the horizontal part 240A, a base layer 280 of a high speed transistor is provided across on a part between the horizontal part 240A and the slope 240B, and the base layers 270, 280 are formed by implanting ions into the epitaxial layer 240 through an oxide film. Owing to the film thickness difference of the oxide film between the horizontal part 240A and the slope 240B, the base layers 270, 280 different in base width can be formed at once by a common ion implanting process.
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