HfO₂-based ferroelectrics for next-generation multi-level non-volatile memory: From fundamentals to prospects

Ferroelectric memory has emerged as a highly promising candidate for next-generation non-volatile memory, offering ultra-low power consumption, ultrafast read/write speeds, high reliability, and significant potential for high-density integration. Over the past fifteen years in particular, the discovery of ferroelectricity in HfO₂-based thin films has attracted widespread attention and stimulated substantial progress in this field. Previous review articles have provided comprehensive summaries of representative advances in the field, covering topics including the origin of ferroelectricity in HfO₂, deposition methods, the performances of HfO₂-based ferroelectric thin films and memory devices, as well as progress in device physics, integration strategies, and emerging applications. However, more recent breakthroughs in the multi-level devices have not yet been systematically reviewed. These developments are becoming increasingly critical for mass data storage and emerging paradigms such as in-memory computing. In this review, we summarize recent progress in HfO₂-based ferroelectric multi-level memories, with a focus on material studies, device designs, and emerging applications. By highlighting these advances, we aim to delineate both the persistent challenges and opportunities associated with this technology, with the goal of inspiring further innovation in the field.