A method of manufacturing a vertical semiconductor device includes preparing a semiconductor wafer which has a heavily doped semiconductor substrate and a lightly doped semiconductor layer disposed over the semiconductor substrate, forming a semiconductor element at a surface portion of the semiconductor layer, forming a first metal layer for a first electrode of the semiconductor element over the surface portion of the semiconductor layer, grinding a back of the semiconductor substrate to thin the semiconductor substrate and roughen a back surface of the semiconductor substrate, performing a wet etching upon the back surface; and forming on the back surface a second metal layer for a second electrode of the semiconductor element.