Abstract In this work, a narrowed Si_0.7Ge_0.3 channel FinFET device using a precise cyclic wet treatment process is demonstrated in detail. Si_0.7Ge_0.3 fin/per side of 0.63nm can be accurately removed in each cycle by utilizing a self-limited oxidation with 40% HNO₃ solution for 40 s and oxidation removal with 1% HF solution for 10 s. As a result, after the dummy gate removal, the fin width of Si_0.7Ge_0.3 can be narrowed from 20nm to 8nm by utilizing 10 cycles of this wet treatment process. Compared with the conventional Si_0.7Ge_0.3 FinFET under the similar process, the narrowed Si_0.7Ge_0.3 channel FinFET using this newly developed wet treatment process can realize a stronger gate control capability because its subthreshold slope can be reduced by 24%, improved from 87 to 64 mV/dec.