The effects of adding C2H4on the chemical vapor deposition (CVD) of SiO2films from SiH4/O2were studied at temperatures ranging from 673 to 1073 K using a hot‐wall‐type tubular reactor. Adding C2H4improved the step coverage of the films while effectively suppressing the gas‐phase formation of particles. Because C2H4is a well‐known radical scavenger, the control of gas‐phase chain reactions by consuming atom and/or radical species is responsible for the suppression of particle formation. Comparison of the sticking probability of growth species in SiH4/O2systems with and without added C2H4shows that high deposition temperatures are responsible for the improvement in step coverage. The analysis of the carbon content in the films by x‐ray photoelectron spectroscopy (XPS) shows no difference in carbon impurity levels between the SiH4/O2/C2H4and SiH4/O2chemical systems. ©1995 American Institute of Physics.