| 摘要 |
PURPOSE:To isolate a trench which is capable of giving a fixed potential to a buried electric conductor in such a way that a wiring part inside a contact hole does not come into contact with an active region surrounded by a region isolated by the trench by a method wherein more than one insulating film is formed between a second insulating film where the contact hole is to be made and a semiconductor substrate. CONSTITUTION:After a first silicon dioxide thin-film 14 and a silicon nitride (Si3N4) film, to become a third insulating film 2, have been formed selectively on a semiconductor substrate 1 composed of silicon or the like and a third oxide film 3 has been formed on the whole surface, the third oxide film 3 and the third insulating film 2, which are located in a region to make a trench, are removed. Then, after a trench 4 has been made by digging the semiconductor substrate 1 down to a desired depth by anisotropic etching, impurity ions are implanted into the side wall and the bottom of the trench. In addition, a first insulating film 5 is formed on the inner wall of the trench. Then, after the first insulating film 5 on the bottom of the trench has been removed and the inside of the trench has been filled sufficiently with an electric conductor 6, the film which is deposited, as an excess, on the semiconductor substrate 1 is removed, and a second oxide film 7 is formed. In addition, a gate 8, a source 9 and a drain 10 are formed.
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