In order to improve the hygroscopic property of LaON and also maintain its excellent interface quality with Ge, LaON incorporated with Ta is proposed and its hygroscopic and electrical properties are investigated by using dry and wet annealing. It is found that large improvement in hygroscopic property can be obtained by the Ta incorporation, and also the LaTaON film exhibits excellent interface quality with the Ge substrate due to the capability of TaON in blocking elemental inter-diffusions and also the passivation effect of LaGeOxNy formed at the LaTaON/Ge interface. Therefore, LaTaON can be considered as a high-quality gate dielectric in Ge MOS device to achieve excellent interfacial and electrical properties, e.g. in this work: high k value (21.0), low interface-state density (5.94 x 10(11) cm(-2) eV(-1)), low gate leakage current (3.07 x 10(-4) A/cm(2) at V-g = V-fb + 1 V) and high resistance against moisture absorption.