Low-k films with the lowest dielectric constant (k) of 2.36 were prepared to investigate effects of ambient annealing conditions on the electrical and structural properties of the films. The annealing in an N-2 ambient does not affect the methyl groups that bond to Si atoms while it removes thermally unstable methyl fractions, resulting in a large decrease of k value. Annealing in oxygen ambient increases the k value of the film compared to that of the as-deposited sample. The addition of hydrogen in N-2 annealing ambient slightly increases the surface hydrophilicity while the film maintains lower dielectric constant. (c) 2007 The Electrochemical Society.