Abstract: Recently ferroelectric properties have been found in hafnia-based nanosized films. Such films are of the utmost interest for development of a universal memory, which combines the advantages of random access memory and flash memory. The paper studies optical properties of hafnia-zirconium oxide films H-f_xZr_yO₂ and lanthanum-alloyed hafnia-zirconium oxide films La:Hf_xZr_yO₂. Fluctuations of thickness in Hf_xZr_yO₂ do not exceed 3.5%, fluctuations of thickness in La:Hf_xZr_yO₂ films—3.2%. Optical properties are analyzed based on effective-medium theory. According to effective-medium theory data, Hf_xZr_yO₂ films contain 46% HfO₂, 54% ZrO₂, La:Hf_xZr_yO₂ films contain 47.5% HfO₂, 52.4% ZrO₂, 2.5% La₂O₃.