To know the correlation between the surface contamination of semiconductors and electrical properties of semiconductor devices fabricated on the surface, the contamination of chemically etched Si surface was measured by Auger electron spectroscopy (AES) and Schottky contact was formed by evaporation of Au on that surface in situ. The various chemical etchants were used, including HF, HNO3, CH3COOH, their mixture, and alkaline etchant. The saturation current, the barrier height, and the n-value of the forward current-voltage characteristics of Au-Si Schottky contact were used for evaluating device characteristics, and in-depth profile of composition of the metal film on Si was also measuring by AES combined with ion-sputter etching. Following results are obtained; The barrier height of the Au-Si Schottky contact whose Si surface is contaminated by carbon is low and 0.810.02 eV, and not far from that of clean surface. On the other hand that of Si surface not so much contaminated by carbon but by oxygen is large and 0.830.01 eV, and the n-value is close to unity. This phenomena can be explained by assuming the vanishing of surface states of Si surface with small oxygen adsorption. This model cannot be applicable to heavily contaminated surface. The results of composition analysis show that a small amount of oxygen passivates Si surface and gives high barrier height.