In this letter, we demonstrate that formation of a Zr-silicate interfacial layer between ZrO2 and Si substrate can be controlled by the solid state reaction between Zr and an underlying SiO2/Si substrate through in situ vacuum anneals and subsequent UV oxidation. By investigating the chemical shifts of Si 2p, Zr 3d, and O 1s features using x-ray photoelectron spectroscopy, the formation of a Zr-silicide phase after in situ vacuum anneals of the Zr/chemical SiO2/Si gate stack at 200 °C was confirmed. The Zr-silicide was oxidized to form a Zr-silicate phase in the subsequent UV-ozone oxidation treatment. According to spectroscopic analyses, Zr-silicate bonding occurred in the interfacial layer for the in situ vacuum annealed samples. Vacuum annealed samples containing the silicate interface layer exhibited excellent dielectric characteristics, such as negligible capacitance–voltage hysteresis (∼10 mV), lower fixed charge density, and reduced equivalent oxide thickness compared to unannealed samples.