The characteristics of MOS capacitors passivated by ZnF2- and Si3N4-containing ZnO-B2O3-SiO2-Al2O3-P2O5 glasses with a variation in water content were investigated. When the OH- absorption coefficients in the glasses increased, there was an adverse effect on the recovery of hysteresis and C-V curve shifts for the MOS capacitors passivated with them. Water content was related to the nitride concentrations in the ZnO-B2O3-SiO2-Al2O3-P2O5 glasses. Because nitrite ions in glasses exhibited a pyrohydrolysis reaction, they played an important role in decreasing the concentration of OH-ions. A low OH-concentration in the glasses is useful in improving the C-V curves.