| 摘要 |
The method includes forming a pad oxide, a polysilicon layer over a substrate. Next, an oxide layer is formed over the polysilicon layer. An opening is formed in the oxide layer, the polysilicon layer, and the pad layer. A trench is formed by etching the substrate using the oxide layer as a mask. A sidewall structure is then formed on the opening. Next, an exposed portion of the substrate is etched by using the sidewall structure as a mask. The sidewall structure and the oxide layer are then removed. An oxide and an oxynitride layer are then formed on the aforesaid feature. A semiconductor layer is then formed over the oxynitride layer. A portion of the semiconductor layer is oxidized for forming an insulating layer. Finally, a refilling layer is formed over the insulating layer and the substrate is planarized for having a planar surface.
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