Suspended carbon nanotube field-effect transistors fabricated with a dry transfer technique demonstrate strong promise as ultra-low-power, hysteresis-free gas sensors. However, the difficulty of establishing a good electrical contact between a nanotube and the electrode surface often limits the yield of low-resistance devices that can operate as low-power gas sensors. In this work, the contact resistance at the nanotube-metal interface and the distribution thereof are reduced significantly by removing the top layer of electrode surface with Ar-ion etching directly before nanotube placement. Combined with post-transfer annealing, this pre-transfer electrode surface cleaning reduces the median ON-resistance of transistors by an order of magnitude–from 1.56 MOhm to 143 kOhm–and the interquartile range by more than two orders of magnitude–from 9.38 MOhm to 59 kOhm. The ability to consistently improve nanotube-metal contact demonstrated in this work is a significant advance in the fabrication of ultraclean nanotube transistors and carbon nanotube gas sensors.