Indium tin oxide (ITO) films were deposited onto p-type Si wafers with radio frequency (r.f.) magnetron sputtering. The effect of the silicon surface treatment with reactive ion etching (RIE) on the current–voltage (I–V) and capacitance–voltage (C–V) characteristics of the ITO/Si junction are investigated. When the Si substrate is etched by RIE prior to the deposition of ITO film, the I–V characteristics of the ITO/p-Si junction transfer from an ohmic contact for the unetched-Si to a rectifying contact for the etched Si. In addition, the barrier height, ideality factor, and series resistance increase with increasing etching power. This is attributed to the net positive ion charge and defects on the damaged surface. Thermal annealing can eliminate the damage caused by RIE. The I–V curves of ITO/etched p-Si become more ohmic as samples are annealed in N2 at 300 °C. Secondary ion mass spectroscopy (SIMS) depth profiles indicate that some impurity defects migrate and/or disappear after post-etching annealing.