Lu ₂ O ₃ thin film was deposited on n -type (100) Si substrates using pulsed laser deposition. A k value of 15.95 with an equivalent oxide thickness (EOT) of 1.10 nm and a current density of 2.6×10^-5 A / cm ² at +1 V accumulation bias is achievable for the 4.5 nm thick Lu ₂ O ₃ thin film deposited at room temperature after postdeposition annealing at 600 ° C in oxygen ambient. Annealing a similar sample at 900 ° C caused the EOT and leakage current density to increase to 1.68 nm and 1×10^-4 A / cm ² , respectively. High resolution transmission electron microscopy analysis has shown that Lu ₂ O ₃ film remains amorphous at high temperature annealing at 900 ° C . An x-ray reflectivity analysis on a separately prepared sample with lower annealing temperature (800 ° C ) suggested a formation of Lu-based silicate layer. It is believed that the formation of low- k silicate layer may have contributed to the observed increase in EOT and the reduction in the k value.