Multibit Ferroelectric FET Based on Nonidentical Double HfZrO2 for High-Density Nonvolatile Memory

A double-HZO (HfZrO2) FeFET (ferroelectric FET) with nonidentical ferroelectric thicknesses is experimentally demonstrated with as low as $\vert {V}_{P/{E}}\vert = {5}$ V, 2-bit endurance > 105 cycles and retention > 104 s. Inserting an insulator to separate the ferroelectric layers and avoid the monoclinic formation of a thick Fe-HZO (ferroelectric-HZO) is a useful method to enhance the MW (memory window) for MLC (multilevel cell) applications. Double-HZO has a lower ER (error rate) and shows a 600X improvement compared to single-HZO. The stacked HZO FeFET has potential as an MLC for high-density NVM (nonvolatile memory) applications.