The effects of bias power on the pore size, pore distribution, relative dielectric constant (k), density, composition, and leakage current of plasma enhanced chemical vapor deposited (PE-CVD) low-k film were studied. The pore diameter of the PE-CVD film changes from 1.23 to 0.73 nm with the application of bias power from 0 to 100 W. Pores with an average diameter larger than 0.63 nm were found to decrease the k value of the PE-CVD low-k film. The pore volume ratio of the PE-CVD low-k film with different compositions was calculated from the measured pore size, k value, and density. The relationships between the k value and the density, and the calculated pore volume ratio, were estimated with a simple model. The k value and the density were found to increase with increasing silicon and oxygen contents and decreasing hydrogen content in the film at the same pore volume ratio. The pore volume ratio of the PE-CVD low-k film with the lowest k value, 2.66, was estimated as 31% from the relationship between the k value and the calculated pore volume ratio.