We synthesized organic-inorganic hybrid materials (hybrimers) using a simple non-hydrolytic sol-gel reaction and applied the materials as gate insulators in organic thin film transistors (OTFTs). The hybrimer thin films had smooth and hydrophobic surfaces, and were stable with solvents. In addition, the hybrimer thin films had good electrical properties such as low leakage current and high dielectric strength. The performance of the OTFT with hybrimer gate insulator fabricated by drop casting of regioregular poly(3-hexylthiophene) (P3HT) was similar to that of OTFT with hexamethyldisilazane (HMDS) treated thermally grown SiO2. The hysteresis of RR-P3HT based OTFT with hybrimer gate insulator was negligible. (c) 2007 Elsevier B.V. All rights reserved.