AbstractWe have proposed a metal‐gap‐semiconductor (MGS) sensing device. Different concentrations of λDNA solutions have been characterized by capacitance–voltage measurements of the sensing device. Hysteresis due to electron traps and flatband voltage shift due to negative charge are observed in capacitance–voltage curves. As the λDNA concentration increases, the flatband voltage shift toward the positive voltage increases in the concentration between 0.01 and 0.3 µg/µl. It is suggested that the hysteresis in capacitance–voltage curves arises from the capture and emission of electrons through the states of the λDNA solution, and the flatband voltage shift is attributed to the charge of the λDNA solution. Copyright © 2008 John Wiley & Sons, Ltd.