| 摘要 |
PURPOSE: A method for fabricating a bipolar junction transistor(BJT) is provided to simplify a fabrication process and obtain a high cut-off frequency by fabricating a BJT of a bipolar complementary metal oxide semiconductor(BiCMOS) structure by using a silicon-on-insulator(SOI) type. CONSTITUTION: Oxygen ions are implanted into a semiconductor substrate(1) to form a buried oxide layer(2). An oxide layer(4) of a predetermined thickness is formed on the SOI layer(3) made of the buried oxide layer. Polysilicon of a predetermined thickness is formed on the SOI layer. A photoresist layer mask pattern for forming a base region on the polysilicon is formed. The polysilicon is etched and the photoresist layer mask pattern is eliminated. P-type impurity ions having a density not higher than a critical density are implanted into the front surface of the resultant structure. The second polysilicon(6) of a predetermined thickness is deposited on the resultant structure. P-type impurity ions having a density not higher than a critical density are implanted into the front surface of the second polysilicon. A predetermined portion of the second polysilicon is etched to form the second base polysilicon pattern partially covering the upper portion of the first base polysilicon. N+ ions are implanted into the SOI layer to perform an annealing process while the first and second base regions are masked by a photoresist layer.
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