The mechanical strength of an organic silica low dielectric constant film was enhanced by introducing a reinforcement monomer into a matrix monomer under plasma polymerization deposition. The modulus improvement mechanism was investigated by using pyrolysis gas chromatography and mass spectrometry. Incorporation of a reinforcement monomer in the film matrix through copolymerization reactions was confirmed. Compositional analysis of the films showed that the extent of reinforcement was associated with the copolymerization ratio and the monomer content in the film. It is also found that the modulus enhancement depends on the content of three-dimensional aromatic bridged structure. (c) 2007 The Electrochemical Society.