In the present work, we examine the effect of structural modifications occurring during the fabrication of Al/Yb2O3/SiO2/n-Si/Al MOS capacitors under different annealing temperatures on the electrical characteristics of the capacitors. The structural properties depending on post-deposition annealing (PDA) were evaluated based on the crystal properties, elemental compositions, and bonding structures of Yb2O3/SiO2 films, while the electrical characteristics were determined by capacitance-voltage (C-V) measurements. The smallest particle size was found in the film annealed at the highest PDA temperature. In all films, the Yb atom concentration was determined higher than the others. The non-stoichiometric silicate (YbSixOy) layer was detected in film structure annealed at 400 degrees C. The Yb 4d and O 1s spectra shifted toward higher binding energies with increasing depth in the films. The density of bonded oxygen species decreased with increasing PDA temperature. It was obtained that capacitance in accumulation region (C-acc), dielectric constant (epsilon(k)), and series resistance (R-s) values tend to decrease with both increasing frequency and PDA temperature. The highest and lowest interface state density (N-it) was found for capacitors obtained from as-deposited and annealed at 400 degrees C structures, respectively. The effective oxide charge density (Q(eff)), which expresses the net charge trapped in the oxide layer, is at the 10(11) level. The barrier heights (phi(B)), which generally tend to increase, have shown that acceptor-type interface states are active on electrical characteristics.