Two-dimensional (2D) semiconductors are attractive channels to shrink the scale of field-effect transistors (FETs), and among which the anisotropic one is more advantageous for a higher on-state current (I_on). Monolayer (ML) SnSe₂, as an abundant, economic, nontoxic, and stable two-dimensional material, possesses an anisotropic electronic nature. Herein, we study the device performances of the ML SnSe₂ metal-oxide-semiconductor FETs (MOSFETs) and deduce their performance limit to an ultrashort gate length (L_g) and ultralow supply voltage (V_dd) by using the ab initio quantum transport simulation. An ultrahigh I_on of 5,660 and 3,145 µA/µm is acquired for the n-type 10-nm-L_g ML SnSe₂ MOSFET at V_dd = 0.7 V for high-performance (HP) and low-power (LP) applications, respectively. Specifically, until L_g scales down to 2 and 3 nm, the MOSFETs (at V_dd = 0.65 V) surpass I_on, intrinsic delay time ( $\tau$), and power-delay product (PDP) of the International Roadmap for Device and Systems (IRDS, 2020 version) for HP and LP devices for the year 2028. Moreover, the 5-nm-L_g ML SnSe₂ MOSFET (at V_dd = 0.4 V) fulfills the IRDS HP device and the 7-nm-L_g MOSFET (at V_dd = 0.55 V) fulfills the IRDS LP device for the year 2034.

Moore's law is approaching its physical limit. Tunneling field-effect transistors (TFETs) based on 2D materials provide a possible scheme to extend Moore's lawdown to the sub-10-nm region owing to the electrostatic integrity and absence of dangling bonds in 2D materials. We report an ab initio quantum transport study on the device performance of monolayer (ML) black phosphorene (BP)TFETs in the sub-10-nm scale (6–10 nm). Under the optimal schemes, the ML BP TFETs show excellent device performance along the armchair transport direction.The on-state current, delay time, and power dissipation of the optimal sub-10-nm ML BP TFETs significantly surpass the latest International Technology Roadmap for Semiconductors (ITRS) requirements for high-performance devices. The subthreshold swings are 56–100 mV/dec, which are much lower than those of their Schottky barrier and metal oxide semiconductor field-effect transistor counterparts.