Abstract: This study examined HfAlO_x gate dielectric films with varying Hf to Al precursor ratios using atomic layer deposition (ALD) technology. The chemical composition, surface morphology, optical properties, and dielectric characteristics of these films were systematically analyzed. The findings revealed that HfAlO_x exhibits high optical transmittance and a smooth surface morphology, with significant changes in dielectric properties as the proportion of Al increases. To fabricate high-performance low-voltage-operated field-effect transistors (FETs), InCaO_x nanofibers prepared via electrospinning were employed as channel materials, while HfAlO_x thin films deposited by ALD served as gate dielectrics, forming an InCaO_x/ HfAlO_x FET. The results demonstrated that when the Hf to Al precursor ratio was 2∶1, the device achieved optimal performance, including a field-effect mobility of 17.3 cm² V⁻¹ s⁻¹ and a current switching ratio of 1.2 × 10⁷. A load-type inverter was constructed by connecting the best -performing FET and resistor in series, achieving a gain of up to 13.4 and exhibiting favorable dynamic voltage characteristics at a driving voltage of only 3 V. These outstanding results indicate that the low-voltage high-performance InCaO_x/ HfAlO_x FET holds significant potential for applications in microelectronics.