This study proposes a novel approach to achieving highly reliable, low-voltage polarization switching of ferroelectric Hf_0.5Zr_0.5O₂ (HZO) thin films using polymorph- and orientation-controlled W electrodes ((111)-textured α-W and (200)-textured β-W) by adjusting the sputtering conditions. We demonstrated the formation of (111) and (002)/(020)-textured HZO films on the (111)-textured α-W and (200)-textured β-W electrodes, respectively. Under a low-voltage pulse of 1.2 V (1.5 MV/cm), α-W/HZO/α-W and β-W/HZO/β-W capacitors exhibited double-remanent polarization (2P_r) values of 29.23 μC/cm² and 25.16 μC/cm², which were higher than that of the TiN/HZO/TiN capacitor by 33% and 14%, respectively, and a high endurance of 10⁹ cycles without hard-breakdown. The differences in the ferroelectric properties and switching kinetics were understood based on the polymorphism and texture of the HZO films influenced by electrode materials.

(Hf,Zr)O₂ offers considerable potential for next-generation semiconductor devices owing to its nonvolatile spontaneous polarization at the nanoscale. However, scaling this material to sub-5 nm thickness poses several challenges, including the formation of an interfacial layer and high trap concentration. In particular, a low-k SiO₂ interfacial layer is naturally formed when (Hf,Zr)O₂ films are directly grown on a Si substrate, leading to high depolarization fields and rapid reduction of the remanent polarization. To address these issues, we conducted a study to significantly improve ferroelectricity and switching endurance of (Hf,Zr)O₂ films with sub-5 nm thicknesses by inserting a TiO₂ interfacial layer. The deposition of a Ti film prior to Hf_0.5Zr_0.5O₂ film deposition resulted in a high-k TiO₂ interfacial layer and prevented the direct contact of Hf_0.5Zr_0.5O₂ with Si. Our findings show that the high-k TiO₂ interfacial layer can reduce the SiO₂/Si interface trap density and the depolarization field, resulting in a switchable polarization of 60.2 μC/cm² for a 5 nm thick Hf_0.5Zr_0.5O₂ film. Therefore, we propose that inserting a high-k TiO₂ interfacial layer between the Hf_0.5Zr_0.5O₂ film and the Si substrate may offer a promising solution to enhancing the ferroelectricity and reliability of (Hf,Zr)O₂ grown on the Si substrate and can pave the way for next-generation semiconductor devices with improved performance.