Atomically-thin monolayer WS₂ is a promising channel materials for next-generation Moore’s nanoelectronics owing to its excessive theoretical room temperature electron mobility and immunity to quick channel impact. The excessive photoluminescence (PL) quantum yield of the monolayer WS₂ additionally makes it extremely promising for future high-performance optoelectronics. Nonetheless, the issue in strictly rising monolayer WS₂, as a consequence of its non-self-limiting progress mechanism, could hinder its industrial improvement due to the uncontrollable progress kinetics in achieving the excessive uniformity in thickness and property on the wafer-scale. On this examine, we report a scalable course of to attain a 4 inch wafer-scale fully-covered strictly monolayer WS₂ by making use of the in situ self-limited thinning of multilayer WS₂ shaped by sulfurization of WO_x movies. By way of a pulsed provide of sulfur precursor vapor beneath a steady H₂ circulate, the self-limited thinning course of can successfully trim down the overgrown multilayer WS₂ to the monolayer restrict with out damaging the remaining backside WS₂ monolayer. Density useful principle (DFT) calculations reveal that the self-limited thinning arises from the thermodynamic instability of the WS₂ high layers versus a secure backside monolayer WS₂ on sapphire above a vacuum sublimation temperature of WS₂. The self-limited thinning strategy overcomes the intrinsic limitation of standard vapor-based progress strategies in stopping the two^nd layer WS₂ area nucleation/progress. It additionally gives extra benefits, corresponding to scalability, simplicity, and chance for batch processing, thus opening up a brand new avenue to develop a manufacturing-viable progress expertise for the preparation of a strictly-monolayer WS₂ on the wafer-scale.