We have investigated the characteristics of Ta-based amorphous alloy films for use in an x-ray mask absorber. The stress in the TaReGe film can be controlled by changing the concentration of Re, making it easy to obtain low-stress films through deposition with any sputtering system followed by annealing. A required mask contrast can be obtained with a TaReGe film thinner than other Ta-based alloy films because the TaReGe film has a high density and a high mass absorption coefficient. We have achieved 0+/-10 MPa stress control for a TaReGe film by annealing. The TaReGe films showed high durability against various strong acids and developers, and against O-2 plasma. We also demonstrated the fine patterning capability (0.1 mu m) of a TaReGe absorber..