The discovery of ferroelectricity in HfO2 thin film, which is compatible with the CMOS process, has revived interest in ferroelectric memory devices. HfO2 has been found to exhibit high ferroelectricity at a few nanometers thickness, and studies have rapidly progressed in the past decade. Ferroelectricity can be induced in HfO2 by various deposition methods and heat treatment processes. By combining ferroelectric materials with field-effect transistors, devices that combine logic and memory functions can be implemented. Ferroelectric HfO2-based devices show high potential, but there are some challenges to overcome in endurance and characterization. In this paper, we discuss the fabrication and characteristics of ferroelectric HfO2 film and various applications, including negative capacitance (NC)), Ferroelectric random-access memory (FeRAM), Ferroelectric tunnel junction (FTJ), and Ferroelectric Field-effect Transistor (FeFET).

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To improve performances of nonvolatile charge trap flash memory devices, we propose an in situ Hf0.5Zr0.5O2 (HZO)/HfO2/Al2O3 stacked structure, which is compatible for Si with the metal–oxide–semiconductor (MOS) process based on all atomic layer deposition. Since the appropriate bandgap difference between Al2O3 and HfO2, stable charge trap operation is achieved. High-quality ferroelectric HZO film characteristics were showed by minimizing defects and Si diffusion through the sub-layer of Al2O3/HfO2. Therefore, HZO as a blocking layer enhances the memory performance of the charge trap structure due to its specific polarization effect. The proposed device has the high polarization characteristics of HZO (2Pr > 20 μ C/cm2) along with a MOS-cap window (>4 V), good retention capability (>10 years), fast program/erase response operation times (<200 μs), and strong durability (>105 cycles) while operating as a form of single level cell. By comparing Al2O3 and ferroelectric HZO as a blocking layer of the charge trap device, we confirmed that the HZO/HfO2/Al2O3 multi-layer structure had excellent characteristics according to various memory performance indicators. Our proposed high-performance charge trap flash memory can be employed in various applications, including Si-based three-dimensional structures with artificial intelligence systems.