An MOS capacitor type hydrogen gas sensor was fabricated with the structure of Ni/SiO2/Si by using conventional silicon wafer technologies Grown by dry oxidation at 900 C the thickness of the SiO2 film was only 24 A At 150 degrees C comparing to another MOS capacitor with 148 A thick oxide and otherwise identical configurations this sensor showed much faster response speed (the time interval to reach half of the magnitude of the steady state signal or t(50%) was only 4 s in response to 1% H-2 without deduction of the delay from the gas delivery system) as well as enhanced signal magnitude (about two times of the former for 1% H-2) Based on the hydrogen binding to the traps in the bulk SiO2 a mechanism was proposed to explain the very short response time on the device with the ultra thin SiO2 The gate leakage in the device is also discussed The presented sensor demonstrates a promising step in designing low cost H-2 detectors with very fast responses (C) 2010 Professor T Nejat Veziroglu Published by Elsevier Ltd All rights reserved