Abstract: The present invention relates to embedded attenuated phase shift mask blanks for use in lithography for an exposure wavelength of 300 nm or less, and a method of fabricating such mask blanks by ion beam deposition. In particular, the mask blanks comprise a substrate and a thin film system wherein the thin film system comprises a transmission control sublayer comprising one or more metals or metal compounds selected from the group consisting of Mg, Y, La, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Zn, Ge, Sn, Pb, oxides, nitrides, borides and carbides thereof, and combinations of metals and compounds thereof; and a phase shift control sublayer comprising borides, carbides, oxides and/or nitrides of Ge, Si and/or Al or combinations thereof.