| 摘要 |
PURPOSE:To form transistors having different hFE values on a chip simultaneously, by forming a second base region overlapping the emitter region. CONSTITUTION:A second base region 23 overlapping the emitter region 20 is formed. By overlapping the first and second base regions 18, 23, the hFE value is reduced because the impurity concentration is increased and thus recombination current owing to extinction of injected carriers at the base is increased. At this time, the value hFE is varied according to the impurity concentration in the base region 23 and the overlapping area of the emitter region 20 and second base region. In a case where these regions are formed simultaneously in the respective islands 15, 16, the hFE values can be controlled by the overlapping area because of uniform impurity concentrations. Thus a transistor with the maximum hFE value can be formed by a structure having only the first base region 18, and transistors with different hFE values can be formed simultaneously in the respective islands 15, 16 if the overlapping areas are more increased as the hFE values more reduce. |
