| 摘要 |
PURPOSE:To obtain a semiconductor device having a trench capacitor which realizes the breakdown strength characteristic and the leakage-current characteristic which are almost identical to those of a planar capacitor by a method wherein only a corner part, for the trench capacitor, on the surface of a substrate is oxidized selectively so that the part becomes thicker than an insulating thin-film for a capacitor on the sidewall and on the bottom of a groove. CONSTITUTION:After a groove has been made on a semiconductor substrate 1, a silicon nitride film 3 which is formed on the surface of the substrate 1, on the sidewall and on the bottom of said groove through a first thermal oxide film 2 is removed only at a corner part of said groove on the surface of the substrate. Then, the corner part of said groove on the surface of the substrate is thermally oxidized by making use of said silicon nitride film 3 as a mask; the silicon nitride film 3 and the first thermal oxide film 2 which are located on the surface of the substrate and on the sidewall and on the bottom of the groove are removed. After that, a capacitor insulating film 7 is formed in such a way that the sidewall and the bottom of said groove are thermally oxidized to be thinner than a thermal oxide film 6 at the corner part of the groove on the surface of the substrate; said groove is buried with an electric- conductive layer 8. The selective oxidation of the corner part at said groove is executed at an oxidation temperature of, e.g., higher than 900 deg.C.
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