Si-rich SiO2 (SRSO) films were prepared by RF magnetron sputter techniques, and the structural and optical features of nanocrystalline Si (nc-Si) embedded in the SiO2matrix were investigated in terms of post-deposition heat-treatment conditions. The SRSO thin films exhibited PL phenomena in the wavelength range of (450 ~ 500 nm). Post-deposition heattreatment at relatively high temperature like 1000 ~ 1100 °C increased the crystallinity of the films as well as the volume of the Si nanocrystallites (and SiO2), and as a result, PL intensity was enhanced in the visible light region. The nc-Si embedded in SiO2matrix is a few nanometers in size. It is believed that the Si nanocrystallites in the post-deposition annealed films are isolated and well passivated by SiO2.