We have developed high performance amorphous silicon thin film transistors by catalytic chemical vapor deposition (Cat-CVD) method. The amorphous silicon films deposited at a high rate (1.9 nm s - 1 ) have shown a low spin density (1.6x10 1 6 cm - 3 ), measured by electron spin resonance. Thin film transistors, with a field effect mobility of approximately 0.85 cm 2 V - 1 s - 1 , were obtained with the gate SiN x and phosphorous-doped amorphous silicon layers also fabricated by Cat-CVD.