A functional type metal-oxide-semiconductor (MOS) based capacitor was fabricated and studied by using aluminium zirconium oxide (AlxZryOz) as a potential high dielectric constant (k) gate oxide, which was transformed from as-sputtered Al-Zr alloy after undergoing a wet oxidation at 400 degrees C, 600 degrees C, 800 degrees C, and 1000 degrees C in the presence of nitrogen as a carrier gas. A mixture of tetragonal ZrO2-monoclinic Al(x)Zr(y)O(z)phases were present at 600 degrees C while stablized tetragonal Al(x)Zr(y)O(z)phases were detected at higher temperatures with a minute micro strain change. The largestkvalue (21) was obtained by the film oxidised at 600 degrees C, followed by 800 degrees C while the lowest one at 1000 degrees C. The discrepancy was due to the absence of tetragonal ZrO(2)in the latter films. The attainment of akvalue closer to the reported value for ZrO(2)at 600 degrees C suggested that the tetragonal ZrO(2)phase was one of the factors yielding a highkvalue at 600 degrees C. However, further investigation was required for this sample because the slow trap density and total interface trap density was high despite a highkvalue, mainly attributed to the presence of negatively charged traps as the scattering centre in the film. The film obtained at 1000 degrees C was not encourageable to be deployed as a passivation layer for Si MOS device due to its lowkcontrolled by the thick interfacial layer.