In this study, the effects of fluorine (F) plasma pre-treatment with different exposure time on electrical properties of high-κ-based InP metal-oxide-semiconductor capacitor device were investigated. With the optimal F plasma pre-treatment on InP surface for 3 min, the device characteristics including the frequency dispersion, leakage current density and interface trap density were significantly improved due to the optimal F plasma that suppressed the formation of the native oxides by forming strong In-F bonds and passivated the interface traps at the high-κ/InP interface. The present results show that the approach of appropriate F plasma pre-treatment provides a solution for future applications of high-performance InP MOS devices.