Conventional semiconductor fabrication methods are unsuitable for manufacturing two-dimensional material-based devices owing to the possibility of material contamination or damage, which significantly affects the device properties. In this study, the self-aligned contact doping method and remote oxygen plasma treatment were used to fabricate a WSe 2 -based topgate field-effect transistor (FET) with minimal contamination and damage. The results of Raman spectroscopy and capacitance−voltage measurement indicated that neither the WSe 2 nor the gate dielectric was damaged by the remote oxygen plasma. Additionally, the current−voltage measurement results exhibited excellent on/off ratio and field-effect mobility. The developed method can be used to fabricate FETs which have significantly high carrier concentrations and derive excellent electrical characteristics from WSe 2 -based devices. Therefore, the proposed process can serve as an effective device manufacturing method in the future.