Ferroelectric materials have been utilized for non-volatile memory applications [1]. Recently, Al1-x Sc x N (ASN) films were reported to exhibit ferroelectricity with a high remnant polarization of over 100 µC/cm2 which is attractive for future non-volatile memory [2]. The feasibility of FeRAM application has been confirmed based on material and electrical properties [3]. One of the issues of ASN films is the lack of reliability and endurance properties, as the number of switching cycles of 104 to 105 is the typical endurance of the ASN films before breakdown [4]. In this study, we infer the gradual change in the ASN film upon switching cycles.A 50-nm-thick ASN film with x of 0.22 was characterized with TiN electrodes at top and bottom. The as-fabricated film is self-polarized in an upward direction; the negative voltage applied to the top electrode triggers the switching reversal. Capacitance-voltage (C-V) characteristics, double sweeping the voltage to the negative, and then to the positive directions, were used to observe the switching voltage. A sinusoidal wave with an amplitude of 28 V at 2 kHz was used to switch the capacitor, ending with a positive voltage applied to the top electrode.The C-V curve for the as-fabricated sample (fresh), shown in figure 1, showed only a single peak capacitance for each sweep. The voltage at the peak capacitance during the negative sweep shifted from -20.8 to -17.4 V from the first to third sweep, larger than the shift during the positive sweep. This indicates that the switching voltage, or the coercive field, was reduced during the first negative sweep. After stressing the sample by 103-cycle switching, the C-V curve revealed two capacitance peaks in the negative direction, as shown in figure 2; the peak at -20.2 and -15.2 V are referred to as the peaks obtained in the first and third sweeps for the fresh device. The capacitance peak at -20.2 V gradually decreased moving to merge to the peak at -15.2 V. During this transition, little change of the peak in the positive region was observed, indicating that a gradual transformation in the ASN film upon switching reversal is happening only when the film is switched from upward to downward direction. We hypothesized the creation of nitrogen-vacancy (VN) during the switching, facilitating the movement of N atoms to reduce the coercive field. One can understand that the transformation is completed during the C-V measurement for the fresh sample as the time for the measurement is long.In conclusion, we observed a gradual change in the switching voltage upon switching reversal. A lower coercive field was found to gradually appear after switching, decreasing, and shifting the initial coercive field.