| CPC H01L 21/76883 (2013.01) [H01L 21/76898 (2013.01); H01L 23/5283 (2013.01); H01L 23/53271 (2013.01); H10B 12/482 (2023.02); H10B 12/485 (2023.02); H10B 12/488 (2023.02)] | 13 Claims |

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1. A method for manufacturing a semiconductor device, comprising:
providing a substrate having at least one trench;
forming a first polysilicon layer in the trench, covering a sidewall and a bottom of the trench, and not fully fills the trench;
annealing the first polysilicon layer; and
forming a second polysilicon layer at a region of the trench where the first polysilicon layer is not filled after annealing;
wherein
forming the first polysilicon layer, annealing and forming the second polysilicon layer are completed in a same process.
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