We demonstrate that a high quality metal organic chemical vapor deposition (MOCVD) HfAl(x)O(y) (hereafter HfAlO) dielectric film can successfully be deposited with a wide range of composition controllability between HfO(2) and Al(2)O(3) in HfAlO using a single cocktail liquid source HfAl(MMP)(2) (OiPr)(5). A composition ratio between 45 to 90% of HfO(2) in HfAlO is achieved by controlling deposition process parameters. The effect of the composition ratio between HfO(2) and Al(2)O(3) on the electrical properties of the film is also investigated. The HfAlO film with 90% HfO(2) (10% Al(2)O(3)), which has minimum sacrifice of K value (around 19), shows a great improvement in thermal stability and significant reduction of interfacial layer growth during subsequent thermal processes, leading to the reduction in leakage current by around 2 orders of magnitude compared to pure HfO(2) film. The HfAlO film also shows good compatibility with TaN metal gate electrode under high temperature annealing process.