| 摘要 |
PURPOSE:To avoid abnormal exudation of an impurity even if high temperature heat treatment is applied by a method wherein the impurity which is automatically doped laterally from a high density diffusion layer of the first conductive type which is to be an element separation region is absorbed by a low density diffusion layer of the second conductive type. CONSTITUTION:After an N<+> type buried region 22 is selectively formed on a surface of a substrate 21, a P<+> type buried region 23 is selectively formed. An N<-> type diffusion layer (a low density diffusion layer of the second conductive type) 24 is formed between the regions 22 and 23 by the overall ion implantation of phosphorus. With this constitution, when an N<-> type epitaxial layer 25 is formed in the next process, the P-type impurity automatically doped laterally from the region 23 is absorbed by the diffusion layer 24. Therefore, abnormal exudation of the impurity is avoided even if high temperature heat treatment is applied in the next process. |
