Bottom-gate amorphous silicon thin-film transistors were fabricated using active layers deposited by r.f. and hot-wire (HW) chemical vapor deposition on polyethylene terephthalate (PET) and polyimide (PI) substrates. The maximum processing temperature was 100 degreesC for PET and 250 degreesC for PI. For transistors deposited at 100 degreesC by r.f. on PET and at 175 degreesC by HW on PI the transistor characteristics are comparable, although still inferior, to those of standard amorphous silicon transistors fabricated on glass substrates at 250 degreesC. HW transistors fabricated at 100 degreesC showed poor device characteristics. For devices fabricated at 100 degreesC, an extended anneal at this temperature was required to improve the transistor characteristics, independently of the film deposition technique used. (C) 2003 Elsevier Science B.V. All rights reserved.