NOVELTY - The device comprises a reaction chamber (2) for receiving a substrate (20) during the treatment process, a vapor source for generating a vaporous particle stream, and a separator comprising a separation vessel to remove vapor particles from the reaction chamber. The separation vessel has separation stages that are separated by a baffle plate, and comprises an inner container that is removed from the separation vessel by a closable opening of the separation vessel. The baffle plate is helical shaped so that successive turns of the baffle plate form successive separation stages.    USE - The device is useful for treating a coating applied on a surface of a substrate with vaporous particle stream in the manufacture of thin film solar cells.    ADVANTAGE - The device ensures effective, economical and rapid treatment of the coating applied on the surface of the substrate in a simple manner thus improving energy conversion efficiency and service life of the solar cells.    DETAILED DESCRIPTION - The device comprises a reaction chamber (2) for receiving a substrate (20) during a treatment process, a vapor source for generating a vaporous particle stream, and a separator comprising a separation vessel to remove vapor particles from the reaction chamber. The separation vessel has separation stages that are separated by a baffle plate, and comprises an inner container that is removed from the separation vessel by a closable opening of the separation vessel. The baffle plate is helical shaped so that successive turns of the baffle plate form successive separation stages, and comprises a helical cooling coil. The inner container and/or the baffle plate consist of a copper alloy, are provided with a nickel coating, and are cooled. Walls of the separation vessel are cooled. An inlet channel of the separator is heatable.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic cross-sectional view of a device for treating a coated substrate.    Reaction chamber (2)    Substrate (20)    Surface of the substrate (21)    Thin layer (22)    Vacuum pump. (26)