A method for manufacturing a rectifier with a vertical MOS structure is provided. A first trench structure and a first mask layer are formed at a first side of the semiconductor substrate. A second trench structure is formed in the second side of the semiconductor substrate. A gate oxide layer, a polysilicon structure and a metal sputtering layer are sequentially formed on the second trench structure. The rectifier further includes a wet oxide layer and a plurality of doped regions. The wet oxide layer is formed on a surface of the first multi-trench structure and in the semiconductor substrate. The doping regions are formed on a region between the semiconductor substrate and the second trench structure, and located beside the mask layer. The metal sputtering layer is formed on the first mask layer corresponding to the first trench structure.