A method of treating a skin tissue area (3) having a skin surface (5) is provided. The method comprises the steps of: deforming the skin tissue area into a deformed shape comprising a plurality of folds (17) in the skin tissue area; arranging radiofrequency electrodes (13) in contact with the skin surface on opposite sides of the deformed skin tissue area; and, while maintaining the skin tissue area in said deformed shape, providing a spatially continuous radiofrequency energy flow between the radiofrequency electrodes on opposite sides of the deformed skin tissue area through the deformed skin tissue area, thereby heating at least a portion (19) of the deformed skin tissue area; and releasing the skin tissue area from said deformed shape, thereby deforming said heated portion (19) into a wave-shaped zone of heated skin tissue having a depth relative to the skin surface that varies between a minimum and a maximum value in a direction between said opposite sides. Accordingly, an apparatus for treating a skin tissue area (3) is provided.