A novel approach to covalently attached polymer films by surface functionalization and hydrosilylation reaction with reactive polymers on the surface is reported. Stable, uniform, and highly sensitive thin film sensors can thus be fabricated. The covalent attachment of polymer through a silane linker results in films with high uniformity, stability, and reasonable reproducibility as far as film thickness is concerned. Incorporation of molecular recognition reagents into the sensing film increases the sensor sensitivity dramatically, which is critical for detecting vapors such as certain explosives at parts per thousand or parts per billion levels. The sensors fabricated can detect o-nitrotoluene, a TNT simulant, at parts per billion concentrations.