The ion assisted wet removal of (HfO2)(x)(SiON)(1-x) high dielectric constant (k) materials and its effect on electrical properties were investigated. Crystallization temperature of (HfO2)(x)(SiON)(1-x) increased as the percentage of SiON increased. The crystallized (HfO2)(0.6)(SiON)(0.4) was damaged and turned to an amorphous film via incorporation of N species into the film by N-2 plasma treatment. In addition, the structure of (HfO2)(0.6)(SiON)(0.4) was disintegrated into HfO2, SiO(N), and ON after N-2 plasma treatment. N2 plasmas using low bias power were applied for wet removal of high-k films and the mechanism of the ion assisted wet removal process was explored. When high bias power was applied, the surface of source and drain regions was nitrided via the reaction between N and Si substrates. Feasibility of the low bias power assisted wet removal process was demonstrated for short channel high-k metal oxide semiconductor device fabrication by the smaller shift of threshold voltage, compared to the high bias power assisted wet removal process as well as the wet-etching-only process. (c) 2007 American Vacuum Society.