Surface micromachining is used with amorphous and microcrystalline silicon films to form bridge and cantilever structures. Low temperature processing (less than or equal to 350 degrees C) allowed fabrication of structures and devices on glass substrates. Two processes involving different materials as the sacrificial layer are presented: silicon nitride and photoresist. As an example of one possible device application of this technology, a bottom gate air-gap thin film transistor is presented. (C) 1999 Elsevier Science S.A. All rights reserved.