The purpose of this investigation is to study the electrical properties of the YBCO/YSZ/Si metal‐insulator‐semiconductor structure and the yttria‐stabilized zirconia (YSZ)/Si interface. The YBCO and YSZ layers were epitaxially grown in situ on Si by pulsed laser deposition. Current‐voltage measurements of devices fabricated on p‐type Si(100) showed a small leakage current density at 292 K, which decreased further at 80 K. Comparison of capacitance‐voltage measurements at 292 K for frequencies between 10 and 400 kHz showed a large variation of capacitance in the accumulation region demonstrating the presence of mobile ions in the YSZ layer. This variation is less pronounced at 80 K. A negative shift of about 5 V in threshold voltage from 292 to 80 K has been attributed to redistribution of charges in the YSZ buffer layer.