| 摘要 |
PROBLEM TO BE SOLVED: To improve the characteristic of element separation by preventing impurity ions from being taken in an element separation oxidized film, by implanting ions through an anti-oxidized film which is used during formation of the element separation oxidized film so as to form a shallow well in an active area and a deep well in an element separation area respectively. SOLUTION: After a pad oxidized film 2 is formed on a semiconductor substrate 1, a silicon nitride film 3 as an anti-oxidized film is formed. Next an opening is formed in an area in which an element separation oxidized film 5 is formed. Further, impurity ions are implanted into the semiconductor substrate 1 through the silicon nitride film 3 so as to form a well 4. In this case, the well 4 is made shallow in an area where the silicon nitride film 3 is formed and deep in the opening where the silicon nitride film 3 is removed. Thus, the concentration peak of impurity ions in the deep area 4b of the well 4 is under the element separation oxidized film 5 which is formed later, so that the impurity ions are hard to be taken in the element separation oxidized film 5.
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