| 摘要 |
PURPOSE:To obtain a semiconductor device which does not produce a difference in level between a first region and a second region on the surface of an epitaxial layer and which can make the film thickness of said layer different between both regions by a method wherein the epitaxial layer has a surface whose height is the same in the first and second regions and in which a U-shaped stepped part has been formed in the boundary part between both regions. CONSTITUTION:The surface of a p<-> semiconductor substrate 11 is formed to be high in a memory cell region and to be low in a peripheral circuit region. An n<+> type buried semiconductor layer 12 whose thickness is substantially uniform and whose impurity concentration is high is formed on the surface of the p<-> semiconductor substrate 11. Consequently, also the surface of the buried semiconductor layer 12 has a difference in level between the memory cell region and the peripheral circuit region. An n<-> type epitaxial layer 13 whose impurity concentration is low is formed on the surface of the n<+> type buried semiconductor layer 12. Since the surface of the epitaxial layer 13 is formed to be of the same height at the memory region and the peripheral circuit region, the film thickness E1 of the epitaxial layer 13 is thin in the memory cell region and the peripheral circuit region id thick at E2. A U-shaped stepped part 16 is formed in the boundary part between the memory cell region and the peripheral circuit region on the surface of the epitaxial layer 13.
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