A method is provided for forming a polysilicon gate. A stacked gate with a first polysilicon layer/an oxide layer/a second polysilicon layer multiple structure is formed. The invention provides another method for forming a polysilicon gate, in which a first polysilicon layer is formed and waits for a period of time. Then, a second polysilicon layer is formed on the first polysilicon layer. A grain boundary is formed between the first polysilicon layer and the second polysilicon layer. The invention provides still another method for forming a polysilicon gate, in which a polysilicon layer is formed at the temperature of about 600-700.degree. C. and the pressure of about 1-5 torr to form a small-grained polysilicon layer. The three methods for forming a polysilicon gate can prevent the heavy ions from passing through the polysilicon gate and the gate oxide layer into the substrate while performing a pre-amorphization implant process. The absence of these heavy ions in the substrate avoids the subthreshold kink side-effect.