Si/SiO2, Si/Al2O3 and Si/MgO co-sputtered films were prepared by placing 6 or 12 Si plates (5 x 15 mm) on an SiO2, Al2O3 Or MgO target 100 mm in diameter during deposition. X-ray photoelectron spectroscopic (XPS) analysis of these films revealed that the main low valency Si state was SiOx, (0 < x < 2) for Si/SiO2, and Si for Si/Al2O3; and Si/MgO under the same preparation conditions. Although the Si/SiO2 films maintained a homogeneous Si component profile even after heat treatment at 820 degrees C, heat treatment above 700 degrees C for Si/Al2O3 and above 300 degrees C for Si/MgO resulted in an inward diffusion of Si. The Si/SiO2 co-sputtered film had a stronger photoluminescence (PL) intensity at about 1.7 eV than the other two co-sputtered films from Ar ion laser excitation at 514.5 nm. The weak PL observed for Si/Al2O3 and Si/MgO is deduced to be due to the low content of SiOx where electrons and holes recombine and PL is emitted.