| 摘要 |
PROBLEM TO BE SOLVED: To obtain a semiconductor device provided with a bipolar transistor suitable for high frequency having stabilized emitter-base breakdown strength and high frequency characteristics, and a fabrication method thereof. SOLUTION: After native oxide film on a substrate is removed thoroughly by dip etch, a wafer is thrown in at a low temperature of about 400 deg.C and an amorphous silicon film is deposited under a state where oxide film is not present on the surface of the substrate. A base electrode 43 is then formed by patterning and impurities in the base electrode 43 are diffused into the substrate thus forming an external base diffusion layer 41a. Subsequently, an intrinsic base diffusion layer is formed by ion implantation and an emitter diffusion layer 42 is formed by impurity diffusion from an emitter electrode 45. Since an oxide film between the base electrode 43 and the substrate can be reduced, spreading of the external base diffusion layer 41a due to impurity diffusion can be suppressed resulting in the enhancement of emitter-base breakdown strength and high frequency characteristics.
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