We propose employing a p/i/n-type poly-Si thin-film transistor (TFT) for quasi-static capacitance voltage (C-V) measurement. Since the electric current smoothly flows through either the n-type or p-type region, relatively high measurement frequency can be used to observe a quasi-static C-V characteristic for any voltage conditions, which improves the signal-noise ratio. The quasi-static C-V characteristics are available for various analyses such as extraction of trap densities. (c) 2013 Elsevier Ltd. All rights reserved.