In this paper, we present a novel approach toward the fabrication of mechanical oscillators with a local chemical functionalization with subnanometric control. Our method exploits the reactivity of the freshly cleaved surfaces that form when a monocrystalline silicon microstructure is cleaved. The surfaces that form after the cleave expose an atomically smooth Si(1 1 1) surface which, if a suitable chemical environment is provided, could undergo to a cycloaddition process that create stable, local and specific chemical bonds. Here, we demonstrated the feasibility of such a scheme on a twin cantilevers geometry, we prove the effective selectivity and stability of the cycloaddition process and we provide experimental evidence that below a critical size, the cleavage procedure creates step free atomically flat silicon surfaces.