The present paper describes Si microphotonics and its current status of electronics and photonics convergence on Si platform based on monolithic integration using CMOS (Complementary Metal Oxide Semiconductor) technologies. The Si CMOS platform is advantageous over III-V semiconductor based platform because of a short time-lag between basic research and commercialization in terms of the standardized materials and processes. To implement photonic devices on the Si CMOS platform, it is important to reduce materials diversity in current photonics devices. Low loss SiNx waveguides with sharp bends, high performance strained Ge photodetectors for C+L band, and demultiplexer/multiplexer for WDM (wavelength division multiplexing) have been successfully implemented on the Si CMOS platform. The current targets are cost-effective OADMs (optical add-drop multiplexers) for optical communication and optical clocking for Si LSIs beyond Cu-low k technologies.