Abstract: The Polysilicon recrystallizes an d its crystalline grain grows up during the high temperature process of devices.Polysilicon layer is thinned down and removed thoroughly by the high temperature oxidation.High density of stacking faults induced in the silicon substrate act as gettering centers even after the polysilicon is removed.The polysilicon can enhance oxygen pre cipitation nucleating and growing,acting as the intrinsic gettering.The mechanism of the duration of polysilicon gettering is proposed.