The optical properties of (Al2O3)x̸(TiO2)1-x superlattice films have been shown to satisfy the effective medium approximation theory and, therefore, can be tunable. It is found that (Al2O3)x/(TiO2)1-x superlattice films with x=79%–84% as π-phase shifters can be used as high-transmittance attenuated phase-shift mask (HT-AttPSM) blanks at a wavelength of 193 nm. Lower transmittance at an inspection wavelength of 257 nm is desirable for a better inspection. Due to the fact that the transmittance is less than 25% at a wavelength of 257 nm, this means that these layers allow for good inspection. Lower reflectance at an exposure wavelength of 193 nm is desirable, as this leads to better aerial images. To achieve a better aerial image, it is best to select a four-stack (Al2O3)x̸(TiO2)1-x film as the HT-AttPSM blank layer because a four-stack film has the lower reflectance than others. The thickness fraction range of Al2O3 in the four-stack (Al2O3)x̸(TiO2)1-x films used for the HT-AttPSM blanks at a wavelength of 193 nm is found to be between about 79% and about 85%. We fabricate a four-stack (Al2O3- - )x̸(TiO2)1-x film sample for HT-AttPSM that has the optimized optical properties, which include a transmittance of 19.9% and a lower reflectance (3.2%) at a wavelength of 193 nm and a good inspection transmittance (less than 20%) at a wavelength of 257 nm. The four-stack (Al2O3)x̸(TiO2)1-x film can be used to design a desirable HT-AttPSM at the exposure wavelength of 193 nm.