Abstract As the integration of semiconductor chips continued, resistance-capacitance delay emerged and caused deterioration of chip performance. To solve this problem, low dielectric constant (low-k) films with suitable mechanical strengths were required for use as intermetal dielectrics (IMD), and studies have been widely carried out. In this study, low-k plasma polymerized diethoxymethylsilane (ppDEMS) films were fabricated in a plasma-enhanced chemical vapor deposition system with flow rate ratio (FRR) between DEMS precursor and helium (He) carrier gas introduced as a key parameter. As the DEMS/He FRR increased, the refractive index was reduced from 1.401 to 1.386, and the k value decreased from 2.77 to 2.10. The results of Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy showed that the carbon ratio increased and the oxygen ratio decreased, along with a decrease in the film density. With the increased DEMS/He FRR, hardness decreased from 2.5 to 1.8 GPa, and elastic modulus decreased from 17.08 to 11.50 GPa. Leakage current densities for all the ppDEMS films were less than 10-7 A/cm2 at 1 MV/cm. As a result, the ppDEMS films could be suggested as an IMD material, and the DEMS/He FRR could be an effective parameter to control the properties of ppDEMS films.