Fishing – trapping – and vermin destroying
Patent
1990-12-11
1992-03-31
Hearn, Brian E.
Fishing, trapping, and vermin destroying
437 33, 437193, 437194, 437195, 437162, 437909, 148DIG124, 148DIG11, H01L 21265
Patent
active
051008122
ABSTRACT:
According to a method of manufacturing a high-frequency bipolar transistor, a p-type base region is formed on an n-type silicon substrate. A first oxide film and a nitride film are formed on the base region. A base contact hole is formed by etching, and a first polysilicon film containing a p-type impurity and serving as a base electrode is formed thereon. A second oxide film having a thickness larger than that of the first oxide film is formed by thermal oxidation around the base contact hole to surround the first polysilicon film. A portion of the nitride film which is not covered with said second oxide film and a portion of the first oxide film therebelow are removed by etching to form an emitter contact hole. A second polysilicon film including an n-type impurity and serving as an emitter electrode is formed in the emitter contact hole. The n-type impurity in the second polysilicon film is diffused in the substrate by annealing to form an n-type emitter region. In the completed bipolar transistor, the base electrode and the emitter electrode are insulated from each other by the second oxide film.
REFERENCES:
patent: 4729965 (1988-03-01), Tamaki et al.
patent: 4830972 (1989-05-01), Hamasaki
Yamada Yoshiki
Yamaki Bunshiro
Hearn Brian E.
Kabushiki Kaisha Toshiba
Nguyen Tuan
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