NOVELTY - The device (1) has a fluid guidance element (11) whose defined surface structure (13) is configured to provide guidance of process medium (7) along defined surface structure. A flow generating device moves the process medium in intervening space between defined surface structure of fluid guidance element and treatment side of a substrate (5), so that the treatment side of substrate is moved along defined surface structure of fluid guidance element, and defined surface structure of fluid guidance element is moved along treatment side of substrate.    USE - Device for wet-chemical treatment of substrate for use in copper indium gallium selenide (CIGS) solar cell.    ADVANTAGE - The treatment side of substrate is moved along defined surface structure of fluid guidance element, and defined surface structure of fluid guidance element is moved along treatment side of substrate, such that the fluid motion is generated with respect to the substrate. The process medium is distributed by the rollers transversely over the substrate reliably. The reliable coating of substrates is enabled efficiently with buffer layers. The homogeneous flow of the process medium is achieved. The colliding of undesired particles settle in local dead zones is avoided. The necessary exchange of the process medium is significantly prolonged. The simplified structure is achieved. The exit of toxic vapors is avoided. The side edges and side of substrate opposite to treatment side from contact with the process medium is protected.    DETAILED DESCRIPTION - The accommodation device (3) inserts substrate and process medium. The treatment side of the substrate is in operative connection with the process medium. The fluid guidance element has the defined surface structure which is included in accommodation device. An INDEPENDENT CLAIM is included for method for wet-chemical treatment of substrate.    DESCRIPTION OF DRAWING(S) - The drawings show the perspective view and sectional view of the substrate wet-chemical treatment device.    Substrate wet-chemical treatment device (1)    Accommodation device (3)    Substrate (5)    Process medium (7)    Fluid guidance element (11)    Defined surface structure (13)