A silicon photonics-based photodetector (PD) includes a silicon layer on which doped layers of different types are formed on a surface based on a first spacing based on a center line of an optical waveguide through which an optical signal moves, a germanium layer being stacked on an upper part of the silicon layer and formed with doped layers of different types on a surface based on a second spacing based on the center line of the optical waveguide, and a metal electrode configured to generate an electric field by being in contact with the doped layers of the silicon layer and the germanium layer.