The inter-layer dielectric of polysilicon remarkably affects the yield and reliability of charge-coupled device (CCD). In this work, the effects of gate dielectric process on the inter-layer dielectric of the polysilicon of CCD were studied by scanning electron microscopy and electrical measurement system. The results show that the gate dielectric process had significant effects on the morphology of polysilicon inter-layer dielectric. The longer the nitride gate-dielectric oxided, the thicker the polysilicon inter-layer dielectric that located near the gate-dielectric. When the oxidation time of silicon nitride was increase to 320 min, the thickness of inter-layer dielectric of polysilicon near nitride gate-dielectric was increased to 227 nm. After the former-layer polysilicon was oxided, a silicon nitride layer with thickness of 15 nm was deposited, which could fill the viods inside polysilicon oxide near gate-dielectric and no adverse effect on the operating voltage of CCD.