Floating gate fabrication method

A floating gate fabrication method, comprising the following steps in the sequence set forth:

• providing a substrate, and depositing an oxide layer on the substrate;
• fabricating a shallow trench isolation in the substrate, a top surface of the shallow trench isolation being higher than a top surface of the oxide layer;
• depositing a polysilicon layer on the oxide layer and the shallow trench isolation;
• performing a first thermal annealing process on the polysilicon layer, thereby repairing cavities formed after the deposition of the polysilicon layer;
• implanting ions into the polysilicon layer on which the first thermal annealing process has been performed;
• performing a second thermal annealing process on the same polysilicon layer, thereby activating the implanted ions and repairing again the cavities formed after the deposition of the polysilicon layer;
• and
• planarizing the polysilicon layer to form a floating gate.