A new substrate ( ~30-nm HfO2/Si) is developed for high-performance back-gated molybdenum disulfide (MoS2) transistors. Record drain current Ids ~180 μA/μ and transconductance value gm ~75 μS/μm at Vds = 1V have been achieved for 1- μm channel length multilayer MoS2 transistors on HfO2/Si substrate. The transistors on HfO2 substrate show > 2.5× enhancement in field effect mobility ( μFE~65cm2/V·s) compared with the transistors on SiO2 ( μFE~25 cm2/V·s) substrate. The intrinsic mobility extracted from Y function technique ( μFE~154 cm2/V·s) is 3× more than SiO2 substrate. The drastic improvement in transistor performance is attributed to a combination of three factors: 1) efficient gate coupling with an EOT of 6.2 nm; 2) charge impurity screening due to high- k dielectric; and 3) very low contact resistance through sulfur treatment. © 1980-2012 IEEE.