| 摘要 |
PROBLEM TO BE SOLVED: To suppress deterioration of electric characteristics of MOSFET by a method wherein there is formed a structure in which the width of an insulation material buried in an isolation groove of a semiconductor substrate is narrower than that of the insulation material projected from the isolation groove. SOLUTION: A side wall 14 of a width 15 is provided on a side face of an opening part. Namely, after a thermal oxide film 3 is deposited on the entire face of the opening part, the side wall 14 is formed by etching-back. Here, the shape of the side wall 14 after etching back has a curvature. Next, by using a silicon nitride film 2 and the side wall 14 as a mask, a silicon substrate 4 is selectively etched to form an isolation groove 5. Next, a thermal oxide film 6 is formed in an inner wall of the isolation groove 5 by thermal oxidization. At this time, if a thickness 16 of the thermal oxide film 6 is set smaller than the width 15 of the side wall 14, both regions isolated do not invade MOSFET. Accordingly, both actual isolated regions are above the silicon substrate 4, and in other words are an isolation width 1 designed initially, so that deterioration of electric characteristics of the MOSFET is eliminated.
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