Microfabricated SiO2 nanotips are potentially useful as scanning tips in near-field optical microscopy and sensor related functions. We report a process in which the rounding nature of isotropic etching combined with undercutting property of Si(100) are effectively used to microfabricate laterally ordered SiO2 nanotips. Combination of excessive isotropic wet etching of thermally grown SiO2 with anisotropic etching of n-type silicon along (100) planes leads to the formation of nanotips with sharpness; 15 nm. Uniform periodic array of nanotips form due to coalescence of excessively etched SiO2 resulting in nanotips length less than or equal to the separation between the original photolithographic features. Finally, the overall process of nanotip formation is discussed by considering the roles of rapid isotropic etching of SiO2 in buffered oxide etch solution, anisotropic etching of Si(100) in KOH solution, and slow SiO2 etching in KOH solution. (C) 2003 The Electrochemical Society.