Oxide-Semiconductor Channel Transistor DRAM (OCTRAM) with 4F2 Architecture

We successfully demonstrated the world's first 4F² gate-all-around oxide-semiconductor channel transistor DRAM (OCTRAM). In this structure, a high-performance gate-all-around InGaZnO vertical channel transistor (InGaZnO VCT) was integrated on top of an advanced high aspect ratio capacitor. The InGaZnO VCT achieved a high ON current of over $15\mu \mathrm{A}/\text{cell}$ and ultra-low leakage below laA/cell simultaneously. This performance was maintained even after BEOL processing. A 275Mbit OCTRAM array was fabricated with WL 54nm/BL 63nm pitches and showed successful DRAM operation in the designed voltage range, making it a breakthrough technology for future high density 4F²DRAM.