| 摘要 |
A method for manufacturing a semiconductor device in which one active area and another active area formed on an element substrate are electrically isolated from each other includes a first step in which a groove-like area is formed at the element substrate by performing a treatment under conditions whereby the etching rate on a surface {100} is higher than the etching rate on a surface {111} in the area between the one active area and the another active area, and a second step in which the bottom surface of the groove-like area is etched through anisotropic etching. The first step is implemented within a 20 Torr hydrogen gas atmosphere that contains hydrogen chloride gas, and at a temperature of 800 centigrade. The shape of the corner portion formed at the upper end of the trench becomes widened until the angle formed by the side wall and the surface {111} is approximately 144.7 degrees, thereby greatly reducing the concentration of stress at the corner portion. As a result, the shape of the element substrate which is affected by the thermal oxidation is improved to make it possible to reduce the degree to which stress concentrates at the element substrate.
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