The invention provides an MOS device, a manufacturing method of the MOS device and a manufacturing method of two kinds of CMOS devices. The manufacturing method of the MOS device comprises the step of providing a substrate comprising a polysilicon gate, the step of sequentially forming a middle layer, an isolation layer and a first interlayer dielectric layer on the substrate and the polysilicon gate, the step of enabling the upper surface of the first interlayer dielectric layer to be flush with the upper surface of the isolation layer, the step of removing the isolation layer on the polysilicon gate, the middle layer above the polysilicon gate and the polysilicon gate to form a groove, the step of forming a metal grid in the groove, the step of carrying out the planarization processing to enable the upper surface of the metal grid, the upper surface of the first interlayer dielectric layer, the upper surface of the isolation layer and the upper surface of the middle layer to be flush with one another, the step of removing the middle layer on the side wall of the metal grid to form a gap and the step of forming second interlayer dielectric layers on the upper surface of the first interlayer dielectric layer, the upper surface of the isolation layer, the upper surface of the gap and the upper surface of the metal grid. The thickness of the metal grid can be accurately controlled, stray capacitance can be reduced, and the performance of the device can be improved.