In this paper, a post superacid (SA) treatment was proposed to enhance the performance of InAs FinFETs on SiO2/Si substrates. Typically, the subthreshold swing (SS) has reduced from 217 to 170 mV/decade and the transconductance (gm) has increased from 6.44 to 26.5 μS/μm after SA treatment. It was found that the interfacial In2O3 at the InAs/ZrO2 interface was effectively reduced after SA treatment due to the strong protonating nature of the SA solution. As a result, the interface trap density was reduced leading to a pronounced reduction of sheet resistance after SA treatment. The modeling of transfer characteristics indicates that the carrier mobility is enhanced by 5.87.1 folds after SA treatment due to interfacial traps reduction. The results suggest that SA treatment can be potentially extended to other III-V MOSFETs to enhance the device performances.