The paper presents comprehensive studies on the process of the copper-containing active sites formation which are needed for the "direct" synthesis of trialkoxysilanes at the interaction of alcohols with a silicon-based contact mass. These sites are formed during a two step consequent pretreatment of the initial contact mass by hydrogen and argon flow. The so activated samples of contact mass were investigated using HAADF-STEM EDX, EXAFS, XPS and XRD methods. The role of each step of the activation is disclosed. Participation of topochemical and heterogeneous chemical reactions as well as processes of diffusion and sorption-desorption during the active sites formation was found. Based on the retrieved data a new mechanism for the formation of the active sites on the surface of silicon during the activation of the contact mass for the "direct" synthesis of trialkoxysilanes is suggested. (C) 2016 Elsevier Inc. All rights reserved.