| 摘要 |
PROBLEM TO BE SOLVED: To adjust the threshold voltage of a transistor to desired values in a region other than a memory cell region and in the memory cell region by preventing a divot from being formed in a buried oxide film. SOLUTION: A nitride film 30 is formed on a silicon substrate 10 including a first region corresponding to the region other than the memory cell region 3 and a second region corresponding to the memory cell region 4, two adjacent grooves 41 are formed in the first region, and two adjacent grooves 42 are formed in the second region. The nitride film 30 is retracted so that widths W41 and W42 of the grooves 41 increase. At this time, the nitride film 30 on a first portion 11 sandwiched between the first grooves 41 is left and the nitride film 30 on a second portion 12 sandwiched between the second grooves 42 are removed. The grooves 41 and 42 are filled with the buried oxide film 50, and polished using the nitride film 30 as a stopper, and the nitride film 30 is removed. Impurities are implanted into the first portion 11, gate electrodes 71 and 72 are formed on the first portion 11 and second portion 12, and impurities are implanted into the second portion 12. COPYRIGHT: (C)2009,JPO&INPIT
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