In our study, the dielectric properties of SiOC low k thin film derived from polyphenylcarbosilane were investigated as a potential interlayer dielectrics for Cu interconnect technology. A SiOC low k thin film was fabricated onto a n-type silicon wafer by dip coating using 30wt % polyphenylcarbosilane in cyclohexane. Curing of the film was performed in air at 300°C for 2h. The thickness of the film ranges from 1 μm to 1.7 μm. The dielectric constant was determined from the capacitance data obtained from metal/polyphenylcarbosilane/conductive Si MIM capacitors and shows a dielectric constant as low as 3.26 without porosity added. The SiOC low k thin film derived from polyphenylcarbosilane shows promising application as an interlayer dielectrics for Cu interconnect technology.