We developed titanium nitride (TiN) based nanoelectromechanical (NEM) switch with the smallest suspension air-gap thickness ever made to date by a "top-down" complementary metal-oxide semiconductor fabrication methods. Cantilever-type NEM switch with a 15-nm-thick suspension air gap and a 35-nm-thick TiN beam was successfully fabricated and characterized. The fabricated cantilever-type NEM switch showed an essentially zero off current, an abrupt switching with less than 3 mV/decade, and an on/off current ratio exceeding 10(5) in air ambient. Also achieved was an endurance of over several hundreds of switching cycles under dc and ac biases in air ambient. (C) 2008 American Institute of Physics.