We have investigated the effects of high temperature annealing on the physical and electrical properties of multilayered high-k gate oxide [HfSixOy /HfO2 /intermixed-layer(IL)/ ZrO2/intermixed-layer(IL)/HfO2] in metal-oxide-semiconductor device. The multilayered high-k films were formed after oxidizing the Hf/Zr/Hf films deposited directly on the Si substrate. The subsequent N-2 annealing at high temperature (greater than or equal to 700 degreesC) not only results in the polycrystallization of the multilayered high-k films, but, also causes the diffusion of Zr. The latter transforms the HfSixOy/HfO2/IL/ZrO2/IL/HfO2 film into the Zr-doped HfO2 film, and improves electrical properties in general. However, the thin SiOx interfacial layer starts to form if annealing temperature increases over 700 degreesC, deteriorating the equivalent oxide thickness. (C) 2004 American Vacuum Society.