A direct photopatternable organosiloxane-based organic–inorganic hybrid gate dielectric was synthesized. The sol–gel derived hybrid dielectric could be cured at a temperature sufficiently low enough to apply to temperature-sensitive polymeric substrates, whilst maintaining good electrical properties. The addition of hexa(methoxymethyl)melamine minimizes the polar silanol group by enhancing the cross-linking reaction and improves the film density, so that the resulting hybrid dielectric retains both thermal and chemical stability against the highly basic aqueous semiconductor precursor, forming a coherent interface between the dielectric and the semiconductor. The synthesized hybrid materials allow for a high-performance solution-processed flexible ZnO transistor on polymeric substrate at 150 °C.