| 摘要 |
PURPOSE: A method for forming a triple-well of a semiconductor device is provided to permit independent well formation and concentration control without using additional mask processes during an ion implantation process for threshold voltage control of a peripheral PMOS, a peripheral NMOS and a cell NMOS. CONSTITUTION: A field oxide layer(102) is formed on a substrate(101), and then the first and the second oxide layers are respectively formed on the substrate(101) at both sides of the field oxide layer(102). Next, an N-well(106) is formed under the first oxide layer by ion implantation, and the first oxide layer is removed. Next, to form a cell-well(110) inside the N-well(106), the ion concentration of the N-well(106) is changed except a portion where the cell-well(110) will be formed. Next, the cell-well(110) is ion-implanted in consideration of the characteristics of the second oxide layer, and the second oxide layer is removed. Thereafter, ion implantation is performed to form the cell-well(110) along with a P-well(109) under the removed second oxide layer.
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