Electrical and structural characteristics of thin thermally oxidized yttrium layers on Si and on Si covered with 40 A˚ of SiO2have been investigated. The factor of ∼ four advantage in the dielectric constant of Y2O3over SiO2, coupled with extremely low leakage current density of better than 10−10A/cm2in a field of 1.9 MV/cm, sufficiently high breakdown strength, and well‐behaved capacitance‐voltage characteristics makes Y2O3a viable candidate for Si very large scale integration applications, at least in passive devices. High‐resolution transmission electron microscopy reveals the structure of the composite dielectric and provides good agreement between calculated and experimental capacitance.