In the 1550 nm wavelength, which is mainly used wavelength for optical communication, the energy band gap of silicon is 1.1 eV, so that silicon is not proper to detect the light of this wavelength. Nevertheless, research on photodetectors using silicon in silicon photonics has been actively conducted through various approaches. In this thesis, we suggested that an optical silicon waveguide with a high doping PN junction on an SOI wafer can be used as a photodetector. Also, we proposed a junction field effect transistor (JFET) with the same mask with optical components. We suggested a possibility of JFET to be used as transimpedance amplifier of silicon photodetector. Silicon-based photodetector and junction field effect transistor will be used as key devices for monolithic integration of silicon photonics.