| 摘要 |
PROBLEM TO BE SOLVED: To lessen a mask process without decreasing the number of masks, by a method wherein a first conductive type well is formed on a second conductive type shield area of a cell area and a peripheral area, and a second conductive type well is formed on a first conductive type buried area. SOLUTION: An n shield area 23 is formed at a specified depth of a semiconductor substrate 21 in which a cell area and a peripheral area are defined, and n shield sidewalls 25a, 25b are formed at a position of a boundary between the cell area and the peripheral area in the semiconductor substrate 21. A p type buried area 27c for isolating the cell area from the peripheral area is formed for shielding the n shield area at a position apart from the n shield sidewall 25b of the n shield area 23. An n well 28 is formed on this p type buried area 27. A first p well 27a is formed in the inside as enclosed with the n shield sidewall 25a and the n shield area 23, and a third p well 27d is formed in a portion enclosed with a buried area 27c, the n well 28 and the n shield sidewall 25a thereon, and the n shield area 23. |
