| 摘要 |
PURPOSE: A method for fabricating an isolation layer of a semiconductor device is provided to prevent a void in a process for forming a filling oxide layer by forming an oxide layer in a trench such that the oxide layer has a sufficient thickness for filling an undercut under a pad nitride layer. CONSTITUTION: A pad oxide layer(200) and a pad nitride layer are sequentially formed on a semiconductor substrate(100). A predetermined region of the pad nitride layer and the pad oxide layer is etched to expose the substrate in a region for the isolation layer(900). The exposed substrate is oxidized to form a sacrificial oxide layer of a bird's beak. The sacrificial oxide layer is eliminated. The exposed substrate is etched to form a trench by using the pad nitride layer as a mask. An oxide layer(700) is formed on the bottom and the sidewall of the trench so that the oxide layer formed on the sidewall of the trench is twice as thick as the pad oxide layer. The filling oxide layer for filling the trench is formed on the substrate. A planarization process is performed to expose the pad nitride layer. The pad nitride layer is eliminated.
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