Amorphous La-doped Al2O3 (La: Al2O3) thin films are deposited on n-type (100) Si substrates by rf magnetron co-sputtering. The composition of the deposited films is measured by energy dispersive x-ray spectroscopy.Capacitance-voltage measurement shows that the dielectric constant k of La-doped Al2O3 films ranges from 8.5 to 11.6 with the increasing La content, and the highest k value of 11.6 is obtained for the 20.14% La content film.In the structure of the Al /La:Al2O3/Si metal oxide semiconductor, the dominant conduction stems from the spacecharge-limited current at different temperatures. In addition, the wavelength dependence of the transmittance is studied by ultraviolet spectroscopy and the band gap of all the deposited films is above 5.5 eV. The results demonstrate that La-doped Al2O3 can meet the requirement of next-generation gate materials.