The invention discloses a metal oxide semiconductor (MOS) device, and further discloses a manufacturing method of the MOS device. A source-drain region comprises a source-drain mixing region located in an active region and a source-drain polycrystalline silicon layer located on the upper portion of the source region. A source electrode and a drain electrode are led out by forming metal contact on a germanium silicon polycrystalline silicon layer outside the drain polycrystalline silicon layer. Because the area of the source and drain mixing region in the active region does not necessarily contain the area of metal contact, the area of the active region can be made minimum, and performance and integration levels of the device can be improved. The MOS device can reduce stray capacitance between the source-drain region and a substrate, and can be suitable for being applied to the field of radio frequency (RF). The junction depth of the source-drain mixing region is shallow and can reduce short-channel effect and relieve serious length of diffusion (LOD) effect. The manufacturing method of the MOS device can adequately solve the problems of difficulties in an etching stop aspect in the process and isolation optimization between the grid electrode and the source electrode and the drain electrode, and reduce the number of metal layers and cost of the whole bipolar complementary metal-oxide semiconductor (BICMOS) technology.