| 摘要 |
PROBLEM TO BE SOLVED: To realize a semiconductor device in which the base width of a bipolar transistor can be decreased and the base resistance can be reduced. SOLUTION: An insulation layer 2 is formed on the surface of a semiconductor substrate 1 and a first conductivity first semiconductor layer 3 having a first opening 5a is formed on the insulation layer 2. The insulation layer 2 is etched through the first opening 5a and a second opening 5b for exposing the surface of the semiconductor substrate 1 is made through the insulation layer 2. In the second opening 5b, a second semiconductor layer 7 having an impurity diffusion coefficient smaller than that of the semiconductor substrate 1 is formed on the surface of the semiconductor substrate 1. A third opening 5c for exposing the first semiconductor-layer 3 is then made by etching the insulation layer 2 in the second opening 5b thereby enlarging the second opening 5b. A first conductivity third semiconductor layer 8a is formed on the second semiconductor layer 7 and, in the third opening 5c, a first conductivity fourth semiconductor layer 9 is formed on the exposed surface of the first semiconductor layer 3 in contact with the third semiconductor layer 8a. COPYRIGHT: (C)2003,JPO
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