| 摘要 |
PURPOSE: A method for fabricating an isolation layer of a semiconductor device is provided to improve the characteristic and reliability by improving an isolation characteristic and by eliminating a parasitic transistor effect. CONSTITUTION: A pad oxide layer(13) and the first nitride layer are stacked on a semiconductor substrate(11). The first nitride layer, the pad oxide layer and a predetermined thickness of the substrate are etched to form the first trench. An oxide layer(19) and the second nitride layer are sequentially formed. The second nitride layer and the oxide layer are etched back to form a space of a stack structure of the oxide layer and the second nitride layer on the sidewall of the trench and the first nitride layer. The bottom part of the first trench is etched to form the second trench on the bottom of the first trench. A doped polysilicon layer is formed. The doped polysilicon layer is etched back to be left on the bottom of the first and second trenches while the doped polysilicon layer is left as a spacer type on the sidewall of the first and second trenches. A buried oxide layer(27) is formed to bury the first and second trenches. After a planarization etch process is performed to expose the first nitride layer, the first nitride layer is eliminated. The third nitride layer spacer is formed on the sidewall of the structure composed of the oxide layer, the second nitride layer, the doped polysilicon layer and the buried oxide layer.
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