A voltage polarity dependent, voltage-induced wetting transition is demonstrated using a liquid metal-oxide-semiconductor (MOS) junction. A droplet of mercury can be made to spread out on an oxidized silicon wafer upon the application of a voltage. The wetting is seen to depend on the doping type and doping density of the silicon—a voltage polarity related asymmetrical electrowetting is observed. Impedance measurements on Al-SiO2-Si MOS capacitors link the space-charge effects with the electrowetting on the Hg-SiO2-Si MOS junction. A modified Young-Lippmann equation for electrowetting at a MOS junction is derived—the model agrees with the experiments