Titanium is a promising new material system for the bulk micromachining of microelectromechanical (MEMS) devices. Titanium-based MEMS have the potential to be used for a number of applications, including those which require high fracture toughness or biocompatibility. The bulk titanium etch rate, TiO2 mask etch rate, and surface roughness in an inductively coupled plasma (ICP) as a function of various process parameters are presented. Optimized conditions are then used to develop the titanium ICP deep etch (TIDE) process. The TIDE process is capable of producing high aspect ratio structures with smooth sidewalls at etch rates in excess of 2 mu m/min, providing a new means for the microfabrication of titanium-based MEMS devices. (c) 2005 The Electrochemical Society.