| 摘要 |
Fabrication method of semiconductor device to reduce leak current at junction interface of p-type well and n-type well. The method includes forming a first trench portion by selective dry etching of a silicon substrate using a first etching gas and forming a second trench portion including an enlarged width portion downward from a bottom of the first trench portion by additional dry etching of a silicon substrate at the bottom of the first trench portion 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 are used in the process to form the second trench portion.
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