Polyphenylsilsesquioxane-b-polycaprolactone (PPSQ-b-PCl) copolymer, to apply as an interlayer dielectric material, was synthesized from condensation polymerization of α, ω-hydroxyl polycaprolactone (PCL) prepolymer and polyphenylsilsesquioxane (PPSQ). PPSQ was prepared from condensation polymerization of phenyltrichlorosilane and phenylenediamine. PPSQ-b-PCL copolymer was spin-coated on ITO glass and cured in an electric furnace that was equipped with N₂ injection port. By curing of the coated material, sphere-shaped pores was obtained by sintering the PCL segment. The structures of PPSQ-b-PCL were confirmed by FT-IR and NMR. Their thermal properties were measured by TGA. Morphology, topography, and dielectric constant, according to the contents of PCL in film, were measured by SEM, AFM, and impedance analyzer.