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Abstract: Amorphous (ZrO2) x –(SiO2)1−x and (Al2O3) x –(ZrO2) y –(SiO2)1−x−y composite films were prepared using r.f. unbalanced magnetron sputtering in an atmosphere of argon and oxygen at room temperature. The (ZrO2) x –(SiO2)1−x and (Al2O3) x –(ZrO2) y –(SiO2)1−x−y composite films were completely oxidized when an O2/Ar flow rate ratio of 2.0 was used. The optical constants of these thin films depend linearly on the mole fraction of corresponding films. By tuning the (x, y) mole fractions of (Al2O3, ZrO2) in the (Al2O3) x –(ZrO2) y –(SiO2)1−x−y composite films, the optical constants can meet the optical requirements for a high transmittance attenuated phase shift mask (HT-AttPSM) blank. The n–k values in the quadrangular area in the (x, y) plane, where x and y represent the mole fractions of Al2O3 and ZrO2, respectively, meet the optical requirements for an HT-AttPSM blank with an optimized transmittance of 20±5% in ArF lithography. It is noted that the quadrangular area is bounded by (0, 0.31), (0, 0.62), (0.26, 0) and (0.57, 0). All the films also met the chemical and adhesion requirements for an HT-AttPSM application. One (Al2O3)0.1–(ZrO2)0.52–(SiO2)0.38 composite film was fabricated with optical properties that meet the optimized optical requirements of ArF-line HT-AttPSM blanks. Combined with these HT-AttPSMs, ArF-line (immersion) lithography may have the potential of reaching 65-, 45-nm and possibly the 32-nm technology nodes for the next three generations. [Copyright &y& Elsevier]