Kuk, Song-Hyeon Kim, Bong Ho Park, Youngkeun Ko, Kyul Hwang, Hyeon-Seong Cho, Byung Jin Han, Jae-Hoon Kim, Sang-Hyeon 2025-06-18T03:00:11Z 2025-06-18T03:00:11Z 2025-06-13 2025-07 0018-9383 https://pubs.kist.re.kr/handle/201004/152625 3-D NAND flash cells with ferroelectric field-effect transistors (FEFETs) have gained significant attention due to emerging challenges in 3-D NAND technology. Although metal-insulator-ferroelectric-insulator-semiconductor (MIFIS) structures provide large memory windows (MWs), FEFET is still under extensive research and faces critical issues such as data retention, write endurance, disturbance, variability, scalability, gate stack thickness, write voltage, and thermal stability of FE-HfO2. Here, we propose a novel gate stack, metal-insulator-high k insulator-ferroelectric-insulator-semiconductor (MIKFIS) to address these challenges. The MIKFIS FEFET achieves a large MW of 12.2 V and demonstrates highly enhanced quad-level-cell (QLC) data retention at both 24 C-degrees and 85 C-degrees. Moreover, MIKFIS offers additional benefits, including reduced monoclinic-(m-) phase formation, reduced gate stack thickness, decreased equivalent oxide thickness (EOT), and enhanced FE switching. The origin of the superior retention of MIKFIS is investigated using a revised measurement technique developed to accurately extract polarization. English Institute of Electrical and Electronics Engineers Superior QLC Retention Enhancement of a Large Memory Window FEFET Through Gate Stack Engineering Article 10.1109/TED.2025.3568755 1 IEEE Transactions on Electron Devices, v.72, no.7, pp.3896 - 3902 IEEE Transactions on Electron Devices 72 7 3896 3902 N scie scopus 001499465500001 2-s2.0-105006894642 Engineering, Electrical & Electronic Physics, Applied Engineering Physics Article STRATEGIES Thermal stability Fabrication Flash memories Capacitance Ferroelectric field-effect transistor (FEFET) ferroelectric HfO2 gate stack design NAND flash Logic gates Hafnium compounds FeFETs Silicon compounds Iron Three-dimensional displays