Boltzmann tails can be cut off in band-to-band tunneling (BTBT). However, despite intensive research on conventional semiconductor heterojunction TFETs, carrier generation at the p-n heterointerface degrades the SS due to the difficulty in reducing the active defect levels at the heterointerface. [4][5][6][7] Here, 2D materials provide an ideal platform for TFETs because the dangling-bond-free van der Waals (vdW) heterointerface minimizes carrier generation and the short tunnel distance at the vdW interface increases the on current. [8,9] To date, n-type 2D-TFETs have been mainly investigated because degenerately doped p + -2D materials, such as Nb-doped p + -MoS 2 , [10,11] intrinsic p + -black phosphorus (BP), [12][13][14][15] and externally doped p + -WSe 2 , [16,17] are available as source materials. Degenerately doped source materials are indispensable for TFETs because their high carrier densities afford sharp SS values as well as high on current by modulating the band alignment only in the channel region, not in the source region. However, contrary to n-type 2D-TFETs, degenerately doped n-type source materials in p-type 2D-TFETs have been very limited. Indeed, only intrinsic n + -SnSe 2 is utilized for the source. [18][19][20][21][22][23] Although there are some reports on p-type 2D-TFETs with nondegenerately doped source materials, [24][25][26][27] electrostatic doping by an additional local gate electrode has been applied to the sources, which causes other problems, such as a complicated device structure and an increase in the parasitic capacitance. Recently, the substitutional doping technique during 2D growth has been intensively investigated. [28][29][30][31][32] However, controlling the dopant concentration and crystallinity is still a major challenge.Other air-stable n + -2D crystals except n + -SnSe 2 are in high demand to extend our knowledge of p-type 2D-TFETs. In general, the source material with a narrow bandgap (E G ) is favorable to TFETs in combination with the wide E G channel material because it reduces the barrier height for BTBT. [2] From this perspective, PtS 2 , one of the noble metal dichalcogenides, is a reasonable candidate because of the narrow E G for bulk PtS 2 that has been reported (0.25 eV from experiments and 0.48 eV from density functional theory (DFT) calculations). [33]