The Brillouin light scattering technique has been used to study the elastic properties of a number of silicon dioxide films deposited by plasma-enhanced chemical vapor deposition on Si substrates. In addition to stoichiometric undoped glass films produced from either silane or tetraethylorthosilicate, we have also studied nonstoichiometric Si-rich films and P-doped films. The phase velocity of both the surface Rayleigh mode and the longitudinal bulk wave in the film material has been measured and the two independent elastic constants c(11) and c(44) have been evaluated. The derived values of the Young modulus and the Poisson ratio show appreciable deviations from the values we measured on thermally grown oxide. Moreover, the evolution of the stress during thermal cycles has been analyzed using the substrate curvature method. This permitted us to estimate the thermal expansion coefficient of the films and to distinguish between the intrinsic and thermal components of the stress.