The electrical characteristics, including current-voltage, capacitance-voltage, hysteresis loops, and interface state density, of liquid-phase-deposited (LPD)-SiO2 grown on p-type (100) indium phosphide substrates with and without (NH4)(2)S-x treatments were investigated. The aqueous solution of hydrofluosilicic acid and boric acid were used as the growth solution for silicon dioxide films. The indium phosphide with ammonium sulfide treatment improves the electrical characteristics. The electrical characteristics depend on the boric acid concentration in the growth solution. The leakage currents can reach 6.24 and 8.14x10(-8) A/cm(2) under positive and negative electric fields at 0.5 MV/cm. The effective oxide charges are -5.33x10(10) C/cm(2). The interface state density is 9.65x10(10) cm(-2) eV(-1) at the energy of 0.67 eV from the valance band. (c) 2007 The Electrochemical Society.