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In this paper, a near-ideal subthreshold swing MoS 2 back-gate transistor with an optimized ultrathin HfO 2 dielectric layer is reported with detailed physical and electrical characteristics analyses. Ultrathin (10 nm) HfO 2 films created by atomic-layer deposition (ALD) at a low temperature with rapid-thermal annealing (RTA) at different temperatures from 200 °C to 800 °C have a great effect on the electrical characteristics, such as the subthreshold swing (SS), on-to-off current (I ON /I OFF ) ratio, etc, of the MoS 2 devices. Physical examinations are performed, including x-ray diffraction, atomic force microscopy, and electrical experiments of metal-oxidesemiconductor capacitance-voltage. The results demonstrate a strong correlation between the HfO 2 dielectric RTA temperature and the film characteristics, such as film density, crystallization degree, grain size and surface states, inducing a variation in the electrical parameters, such as the leakage, D it , equivalent oxide thickness, SS, and I ON , as well as I ON /I OFF of the MoS 2 field effect transistors with the same channel materials and fabrication methods. With a balance between the crystallization degree and the surface state, the ultrathin (10 nm) HfO 2 gate dielectric RTA at 500 °C is demonstrated to have the best performance with a field effect mobility of 40 cm 2 V −1 s −1 and the lowest SS of 77.6 mV −1 decade, which are superior to those of the control samples at other temperatures. The excellent transistor results with an optimized industry-based HfO 2 ALD and RTA process provide a promising approach for MoS 2 applications into the scaling of the nanoscale CMOS process.

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