We have developed a novel Si-based composite thin film for attenuated phase shift mask(APSM) applications at 193/157 nm wavelength. The fabrication involved sputtering deposition, either with dual target or a single composite target. At 193 nm, these thin films show tunable optical transmission and good stability against long term radiation, common chemicals used to strip photoresist, and exhibit good dry etch selectivity to quartz. Specifically, a film with initial transmission of 5.72%,the total increase oftransmission was 0.27% for doses up to 5.4 kJ/cm2. Also, the increase of transmission was 0.19% after 60 mm of cleaning treatment in acid based solution (H2S04H20210:1 at 95°C). The dry etch selectivity over fused quartz was greater than 5:1. The transmission of the films at 193 nm can be tuned from 0 % to 20 % by varying the thin film composition, process gas flow and composition, and deposition pressure. This wide transmission window provides the possible extension down to 157 nm wavelength.