Argon‐ion‐beam sputtering technique has been applied to deposit barium titanate (BaTiO3) films on silicon wafers at room temperature under vacuum, and then Al/BaTiO3/Si structures were fabricated. Results show that the current and capacitance of these devices are sensitive to the change of relative humidity at room temperature, and saturation absorption (response) time as well as humidity sensitivity of the devices depend on the chemical composition of the BaTiO3films. For higher annealing temperature and longer annealing time, the oxygen composition increases while fixed charge density decreases. These changes result in lower humidity sensitivity and longer response time. ©1995 American Institute of Physics.