We report on a simple and versatile way for the modification of surfaces with thin polymer films through the thermally induced generation of surface-attached polymer networks. The system is based on copolymers, which contain a thermally reactive sulfonyl azide derivative that has been incorporated into the polymer chain during a radical copolymerization reaction. The copolymers are spin-coated from solution onto a silicon-wafer, which had been previously modified with an organosilane. Upon heating the sulfonyl azide decomposes, leading to a C-H insertion reaction and, at sufficiently high conversion, network formation. As groups in the forming network also attack the molecules of the surface-attached monolayer, the forming network becomes directly attached to the substrate surface. Following this method thin layers of polymer networks from a variety of polymers with different properties can be attached to the substrate. Furthermore, the process can be used for the generation of microstructures of polymers in hot-embossing processes. Here, cross-linking occurs during the embossing process and dimensionally stable microstructures are formed.