| 摘要 |
PURPOSE: A method for fabricating an isolation layer of a semiconductor device is provided to avoid a dishing phenomenon on the surface of the isolation layer in a polishing process after filling an oxide layer and to increase the effective length of the isolation layer by making the bottom of a trench of a relatively large width have an uneven structure. CONSTITUTION: After a pad oxide layer is formed on a semiconductor substrate(21), the first impurity ions are implanted into the first region of the semiconductor substrate. A pad nitride layer is formed on the resultant structure. A part of the pad nitride layer and pad oxide layer in the first region is removed. A predetermined depth of the semiconductor substrate is etched to form a plurality of sub trenches. A predetermined region of the pad nitride layer and pad oxide layer in the first region and the second region except the first region is eliminated. A predetermined depth of the substrate is etched to the first trench including the sub trench in the first region and to form the second trench in a predetermined region of the second region. An oxide layer is so formed on the resultant structure to fill the first and second trenches. A polishing process is performed to maintain a predetermined thickness of the oxide layer. The pad nitride layer and the pad oxide layer are removed to form the isolation layer(30). The second impurity ions are implanted into the semiconductor substrate in the second region.
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