Large-Scale Implementation of Vertical Sidewall and Vertical Multi-Channel WS Nanosheet Field-Effect Transistors for Area-Efficient Integrated Circuit.

2D materials have emerged as promising candidates for next-generation field-effect transistors (FETs) owing to the atomically thin geometry and excellent electrostatic gate control. Here, double-gate vertical sidewall FETs based on chemical vapor deposition-grown monolayer WS are demonstrated and, for the first time, report vertical multi-channel nanosheet FETs (NSFETs). By implementing a dual-step sidewall profile, steep SiO surfaces are obtained, which enabled seamless WS adhesion and contributed to enhanced device yield. The fabricated vertical sidewall WS FETs exhibited good subthreshold swing (SS) and effectively suppressed short-channel effects at channel length as short as 150 nm. Logic gates including inverters, NAND, NOR, AND, OR, and SRAM are integrated using vertical sidewall and planar WS FETs, validating the feasibility of area-efficient integrated circuit. Furthermore, improved drive current is achieved in vertical multi-channel NSFETs realized by stacking WS channels and employing a gate-all-around-like structure. These results highlight the potential of vertical sidewall FETs for enabling area-efficient, ultra-dense integrated circuits.