| 摘要 |
PURPOSE: A method for manufacturing a semiconductor device is provided to prevent a threshold voltage from varying by forming a threshold voltage control region of uniform impurity density on the entire channel region, and to improve a characteristic of the semiconductor device by preventing concentration of an electric field. CONSTITUTION: After a pad oxide layer and a nitride layer are sequentially deposited and patterned on a substrate(1) to expose a part of the substrate, impurity ions are implanted to the substrate to form the first threshold voltage control region. After a sidewall is formed on a side surface of the remaining nitride layer and the pad oxide layer under the nitride layer, a central portion of the exposed first threshold voltage control region and the substrate under the central portion are etched to form a trench. An oxide layer is deposited on the resultant structure and planarized. The nitride layer, the pad oxide layer and the sidewall are etched to expose the first threshold voltage control region remaining on a side surface part of the substrate while an isolation structure(4) is formed inside the trench. Impurity ions are implanted to the exposed substrate and the first threshold voltage control region(8) to form the second threshold voltage control region(5). A gate oxide layer(6) is formed on the second threshold voltage control region. A polycrystalline silicon layer(7) is deposited on the gate oxide layer and the isolation structure.
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