Low dielectric constant (Low-k) films (SiCOH) were deposited from diethoxymethylsiliane [DEMS; SiH(CH3) (OC2 H5)2] which has two ethoxy groups along with one methyl group attached to the silicon atoms. The deposited films have been characterized for different oxygen flows, ranging from 50 to 250 standard cubic centimeters per minute (sccm). The growth rate is increased with the increasing oxygen (O2) flow. The absorbance spectrum of Fourier transform infrared spectroscopy shows that the frequency of Si-O stretching vibration mode in the SiCOH film is shifted to a higher wave number with the increase of oxygen flow. It is deduced that the oxygen does not participate in a simple oxidative mechanism, and has no apparent impact on the methyl content even if the relative Si-O content of the deposited films is up to an O2/ DEMS flow rate ratio of 1:1. Also, the refractive index is decreased with increasing the oxygen flow and slightly increased with the deposition temperature. The dielectric constant of the SiCOH is investigated between 2.7 and 3.2, depending on the deposition temperature and O2/DEMS flow rate ratio, which is lower than that of the current OSG films (k = 2.9-3.3). SiCOH films deposited with DEMS only exhibit higher mechanical hardness and lower leakage current than those deposited with both DEMS and oxygen.