In order to prevent microroughness generation on the Si wafer surface in buffered hydrogen fluoride (BHF), the addition of a surfactant to BHF was investigated. It was found that microroughness generation on the Si wafer surface in BHF was prevented by adding the several 10 ppm surfactant. Also, the dissolution of Si into BHF from the Si wafer surface was suppressed by adding the surfactant. Microroughness generation was suppressed by lowering the NH4F concentration in BHF and the dissolution of Si depended on the OH- concentration rather than on the HF concentration in BHF. For a wide range of HF and NH4F concentrations in BHF, the hydrocarbon anionic surfactant is effective for the prevention of microroughness generation. The prevention of microroughness generation is explained by the adsorption of the surfactant molecules on the Si wafer surface in accordance with the Langmuir type adsorption equation.