HfO₂-based ferroelectrics have emerged as promising candidates for next-generation memory applications due to their superior scalability and CMOS compatibility. However, the inherent trade-off between polarization characteristics and switching reliability remains a critical challenge. This study presents a systematic investigation of doping and intercalation effects on the continuous modulation of grain size and oxygen vacancies in AlO_x-inserted Hf_0.5Zr_0.5O₂ (HZO) films. Our findings reveal that only 0.1 nm AlO_x insertion layer in HZO can significantly reduce the leakage current (by 2 orders of magnitude) and improve the P_r/E_c value (by 44.6%). Moreover, the field cycling characteristics are enhanced through the suppression of the paraelectric m-phase as well as the balancing of fatigue and wake-up induced phase transitions between antiferroelectric t-phase and ferroelectric o-phase. This work offers valuable insights into the fabrication of high-performance and highly reliable HfO₂-based ferroelectric thin films.