Metal-oxide-semiconductor (MOS) capacitors were fabricated to investigate the plasma damage caused by reactive ion etching (RIE) on (100) oriented silicon-on-insulator (SOI) substrates. The thickness of the top-gate oxide, SOI, and buried oxide layers were 10 nm, 50 nm, and 100 nm, respectively. The MOS/SOI capacitors with an etch-damaged SOI layer were characterized by capacitance-voltage (C-V) measurements and compared to the sacrificial oxidation treated samples and the reference samples without etching. The measured C-V curves were compared to the numerical results from corresponding 2-dimensional (2-D) structures by using a Silvaco Atlas simulator.