| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for forming a shallow trench isolation (STI) on a thin silicon-on-insulator (SOI) substrate. SOLUTION: The method includes steps of depositing a first polysilicon layer, depositing a polish stop layer on the first polysilicon layer, forming a plurality of trenches in the substrate, filling the trenches with silicon oxide, CMP polishing a first part of the silicon oxide layer until the polish stop layer, etching a second part of the silicon oxide layer under the polish stop layer as far as the above position of the first polysilicon layer, removing the polish stop layer, depositing a second polysilicon layer, and forming a polysilicon gate made up of the first and second polysilicon layers. Since well ion implantation can be carried out prior to the gate formation, sacrificial oxide growth and the exposure of STI oxide due to the removal can be prevented and an excessive recess in the STI structure can be eliminated. And seam leakage of the STI oxide caused by a polysilicon side wall present after the polysilicon gate etching can also be avoided.
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