| 摘要 |
PURPOSE: A method for forming an isolation region of a semiconductor device is provided to improve a topology problem in a wide width region of a trench and a void problem in a narrow width region of the trench after performing a planarization process. CONSTITUTION: The first oxide layer and a nitride layer are formed on a semiconductor substrate(11). A hard mask of the nitride layer is formed by performing a photo-etching process. The semiconductor substrate is etched and the first trench is formed by using the hard mask. An oxide layer sidewall is formed at a side of the hard mask by depositing and etching selectively the second oxide layer on the whole surface of the substrate. A polysilicon is formed on the whole surface. A planarization process is performed to expose the oxide layer sidewall. The semiconductor substrate of an edge of the first trench is exposed by etching the oxide layer sidewall. The second trench is formed by etching the polysilicon through the hard mask of the nitride layer. The third oxide layer(18) is deposited on the whole surface and the planarization process is performed. The nitride layer and the first oxide layer are stripped.
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