Novel high-κ thin composite films with excellent breakdown strength were synthesized using nonhydrolytic sol-gel processing. Organic-inorganic hybrid materials with high electronic polarizability were prepared as the matrix material to form a covalently bonded interface with the organically modified barium titanate (TBT) nanoparticles through a chemical cross-linking reaction. To enhance the dispersion stability of barium titanate (BT) nanoparticles in the matrix, the chemical nature of their surfaces was modified using diethyl 3-(trimethoxysilyl)propyl phosphonate (TMSP), which was synthesized by the Michaelis-Arbuzov reaction of chloropropyltrimethoxysilane (CPTMS) with 3-triethyl phosphate (TEP). A high degree of dispersion of the dielectric BT nanoparticles significantly improved the dielectric properties of the final composite films. Because the matrix consists of both silane and halogenated bisphenol A moieties with high electronic polarizability, adjusting the chemical composition allowed tailoring of the dielectric and film properties of the final composite materials.