SiCOH films were deposited with plasma-enhanced chemical vapor deposition USin2 vinyltrimethylsilane (VTMS) as a precursor and CO2 as an oxidant. The properties of the films were compared with those films deposited with VTNIS and O-2. As-deposited films and the films annealed at 360 degreesC have been characterized. The growth rate decreased with increasing substrate temperature and increased with increasing CO2,/precursor ratio and plasma power. The dielectric constant was inversely proportional to the relative carbon content and the films deposited with CO2 had a higher carbon content than those deposited with O-2 It was confirmed that CO, was more effective to increase the carbon content. The refractive index of the as-deposited films was about 1.48-1.49 and decreased to 1.46 after annealing. The reduction of the refractive index was due to the lower density and increased porosity of the film. After annealing, the SiCOH films Showed a low dielectric. constant of 1.9 at optimum condition. (C) 2004 American Vacuum Society.