The aim of this paper is to investigate the frequency-dependent electrical characteristics of the Al/Er₂O₃/SiO₂ /n-Si/ Al MOS capacitor deposited by the e-beam PVD technique. The Er₂O₃/SiO₂ films were annealed in the nitrogen ambient for 30 min at 550 ^oC. The crystal structure and surface morphology of thin films have been investigated by XRD and AFM. The capacitance-voltage(C-V) and conductance-voltage (G/w-V) measurements have been performed in the frequency range of 50kHz-1MHz at room temperature. Furthermore, the frequency effects on the series resistance and interface state density through C-V and G/w-V curves were studied and analyzed. It has been observed that the series resistance gives a peak for each frequency, decreasing and disappearing with increasing frequencies. Also, it has been shown that the density of interface states increases with increasing frequency. The measured and calculated results reveal that the frequency has a significant impact on both R_s and D_it of the fabricated MOS characteristics. These effects are supposed to occur because of the interfacial layer (SiO₂) that is contained in between n-Si and Er₂O₃.

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