A tribochemistry-induced selective etching approach is proposed for the first time to produce silicon nanostructures without lattice damage. With a ~1 nm thick SiO_x film as etching mask grown on Si(100) surface (Si(100)/SiO_x) by wet-oxidation technique, nano-trenches can be produced through the removal of local SiO_x mask by a SiO₂ tip in humid air and the post-etching of the exposed Si in potassium hydroxide (KOH) solution. The material removal of SiO_x mask and Si under low load is dominated by the tribochemical reaction at the interface between SiO₂ tip and Si/SiO_x sample, where the contact pressure is much lower than the critical pressure for initial yield of Si. High resolution transmission electron microscope (HRTEM) observation indicates that neither the material removal induced by tribochemical reaction nor the wet etching in KOH solution leads to lattice damage of the fabricated nanostructures. The proposed approach points out a new route in nondestructive nanofabrication.