Pulsed plasma-enhanced chemical vapor deposition from mixtures containing methylsilane (1MS), dimethylsilane (2MS), or trimethylsilane (3MS), systematically varied the methyl content in the resulting low dielectric constant films. The refractive index was found to depend strongly on methyl content but was relatively independent of the precursor used. However, the precursor used strongly impacted the local bonding structure of these organosilicate glass materials as revealed by Si-29 nuclear magnetic resonance. The variations in local bonding structure did impact film hardness. No significant changes were found for the concentrations of CH3 and Si-CH3 after annealing and relative humidity treatment for all Si:O:C:H films grown from IMS, 2MS and 3MS, which suggests that Si:O:C:H films have high thermal stability and very low moisture uptake. The dielectric constants of 2.4-2.6 were observed after annealing. (C) 2003 American Vacuum Society.