| 摘要 |
PURPOSE: A method for fabricating an LDD(Lightly Doped Drain) MOS transistor of a semiconductor device is provided to improve a refresh time of a large integrated memory device by covering active region with a buffer layer and implanting ion to form the source and the drain of a memory device. CONSTITUTION: According to the method, a gate(220) intervening a gate insulation film(21) on a bottom part is formed on a P-type semiconductor substrate(20) where an active region and an isolation region are formed. And a buffer layer(24) is formed on the substrate including the gate. A lightly doped region(25) is formed by implanting an N-type impurity ion into the active region where the buffer layer is formed. And an insulation film(26) is formed on the buffer film. A side wall spacer(260,240) is formed by revealing a surface of the active region by etching back the insulation film and at the same time by leaving the insulation film and the buffer film on a side of the gate. And, a heavily doped region(27) is formed by implanting an N-type impurity ion into the revealed active region using the side wall spacer.
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