| 摘要 |
PURPOSE: A method for forming a trench of a semiconductor device is provided to optimally round the upper corner of a trench in a trench formation process by performing a rounding oxidation process. CONSTITUTION: A pad oxide layer(12) and a pad nitride layer(14) are formed on a semiconductor substrate(10). By an etch process using a photoresist pattern as an etch mask, the pad nitride layer and the pad oxide layer are patterned to form the first trench with a slope. After the photoresist pattern is eliminated, an oxide layer for a spacer is deposited along the step on the resultant structure. By an etch process without an etch mask, the oxide layer for the spacer and the semiconductor substrate are etched to form the second trench narrower and deeper than the first trench. A part of the oxide layer for the spacer is left on the upper corner of the second trench to form the spacer. After the spacer is removed, a rounding oxidation process is performed on the inner surface of the second trench to form a silicon oxide layer(24).
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