| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that high-frequency characteristics are related to f<SB>T</SB>, the reduction of a capacitance C<SB>BC</SB>between a base and a collector is cited as one of factors largely contributing to an improvement in f<SB>T</SB>, and C<SB>BC</SB>is conventionally reduced by forming a LOCOS (local oxidation of silicon) oxide film to the lower section of a base electrode but the thickening of a film thickness is limited in the conventional high-frequency semiconductor device. SOLUTION: A conductive layer is formed to the lower section of the base electrode, and the same potential as an emitter electrode is obtained. Accordingly, the capacitance between the base and the collector in the LOCOS section is distributed to the capacitance between the base and an emitter and the capacitance between the emitter and the collector, and the substantial C<SB>BC</SB>is canceled. Since a conductive layer is made of polysilicon, the reduction of C<SB>BC</SB>can be realized by a single-layer metallic structure, and the high-frequency semiconductor device is obtained in which high-frequency characteristics such as a gain-bandwidth product, forward transfer gains or the like are improved. COPYRIGHT: (C)2005,JPO&NCIPI
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