This work presents a review of silicon nitride applications in Si photonics and electronics. As the one of the prominent photonics platform, it owes excellent characteristics in optical communication that is complimentary in performance to the silicon-on-insulator (SOI) photonics. In addition, silicon nitride plays also an important role in realizing germanium laser because of its unique behavior in tuning strain. The induced strain varies from high tensile to compressive stress. The induced strain improves the carrier transport in the channel of nFETs or pFETs. The strain provides also the possibility in adjusting the bandstructure of germanium and converts the germanium from indirect-to-direct band-gap material which is fundamental in obtain germanium laser.