Air-stable n-type carbon nanotube field-effect transistors (CNTFETs) were fabricated, with Si3N4 passivation films formed by catalytic chemical vapor deposition (Cat-CVD). Electrical measurements reveal that the p-type characteristics of CNTFETs are converted to n-type after fabricating Si3N4 passivation films at 270°C. This indicates that adsorbed oxygen on the CNT sidewalls was removed during the formation process of the Si3N4 passivation films. In addition, the source-drain current of the n-type CNTFETs does not change over time under vacuum, or in air. Consequently, the n-type CNTFETs are completely protected by the Si3N4 passivation film from further effects of ambient gases. Therefore, Cat-CVD is one of the best candidates to fabricate Si3N4 passivation films on CNTFETs. © 2005 American Institute of Physics.