Si-based photonic materials and devices, including SiGe/Si quantum structures, SOI and InGaAs bonded on Si, PL of Si nanocrystals, SOI photonic crystal filter, Si based RCE (Resonant Cavity Enhanced) photodiodes, SOI TO (thermai-optical) switch matrix were investigated in Institute of Semiconductors, Chinese Academy of Sciences. The main results in recent years are presented in the paper. The mechanism of PL from Si NCs embedded in SiO₂ matrix was studied, a greater contribution of the interface state recombination (PL peak in 850-900nm) is associated with larger Si NCs and higher interface state density. Ge dots with density of order of 10¹¹cm^-2 were obtained by UHV/CVD growth and 193nm excimer laser annealing. SOI photonic crystal filter with resonant wavelength of 1598nm and Q factor of 1140 was designed and made. Si based hybrid InGaAs RCE PD with η of 34.4% and FWHM of 27nm were achieved by MOCVD growth and bonding technology between In-GaAs epitaxial and Si wafers. A 16×16 SOI optical switch matrix were designed and made. A new current driving circuit was used to improve the response speed of a 4×4 SOI rearrangeable nonblocking TO switch matrix, rising and falling time is 970 and 750 ns, respectively.