The metal-catalyst-free growth of carbon nanotubes (CNTs) using chemical vapor deposition and the application in field-effect transistors (FETs) is demonstrated. The CNT growth process used a 3-nm-thick Ge layer on SiO2 that was subsequently annealed to produce Ge nanoparticles. Raman measurements show the presence of radial breathing mode peaks and the absence of the disorder induced D band, indicating single walled CNTs with a low defect density. The synthesized CNTs are used to fabricate CNTFETs and the best device has a state-of-the-art on/off current ratio of 3 x 10(8) and a steep subthreshold slope of 110 mV/decade. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3534829] All rights reserved.