| 摘要 |
Fabrication method of semiconductor device to reduce leak current at junction interface of p-type well and n-type well. The method comprises forming a first trench portion 109 by selective dry etching of a silicon substrate 101 using a first etching gas and forming a second trench portion 113 including an enlarged width portion downward from the bottom of the first trench portion 109 by additional dry etching of a silicon substrate 101 at the bottom of the first trench portion 109 using a second etching gas. A mixture gas of a chlorine gas and a fluorocarbon gas is used as the second etching gas and also a bias voltage lower than that in the process to form the first trench portion 109 are used in the process to form the second trench portion 113.
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