| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor device and its manufacturing method in which the reliability of a gate insulating film of a transistor to which a high voltage is applied is ensured, simultaneously reduction in the current driving capability of the transistor driven at a low voltage is avoided, and further the high integration of the semiconductor device can be attained. SOLUTION: A pad oxide film 11 and a silicon nitride film 12 are formed on a semiconductor substrate 10. Next, after the silicon nitride film 12 is patterned, the pad oxide film 11 and the substrate 10 are etched to form a trench 13a in a first area and a trench 13b in a second area. Thereafter, the second area is protected by a resist, and the pad oxide film 11 of the first area is side-etched to form a gap between the substrate 10 and the silicon nitride film 12. Next, inner surfaces of the trenches 13a, 13b are oxidated. At this time, a relatively large amount of an oxidizing agent (oxygen) is supplied to the upper edge of the trench 13a, to increase a curvature of the edge of the substrate 10. COPYRIGHT: (C)2004,JPO
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