| 摘要 |
In a nonvolatile semiconductor memory device which has a nonvolatile memory cell portion, a low-voltage operating circuit portion of a peripheral circuit region and a high-voltage operating circuit portion of the peripheral circuit region formed on a substrate and in which elements of the above portions are isolated from one another by filling insulating films, the upper surface of the filling insulating films in the high-voltage operating circuit portion lies above the surface of the substrate and the upper surface of at least part of the filling insulating films in the low-voltage operating circuit portion is pulled back to a portion lower than the surface of the substrate.
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