Disclosed is a method and a respective apparatus for ultrasonic wet treatment of a plate-like article, which comprises: bringing a solid element, which is connected to a transducer in close proximity to a surface of a plate-like article so that a gap is formed between the solid element and the plate-like article, the gap having a distance d2 between 0.1 mm and 5 mm, dispensing liquid for filling the gap between the solid element and the plate-like article, and detecting ultrasonic waves and/or controlling the distance d2, by measuring the distance d2, comparing the measured distance with a desired distance d0 and adjusting the distance accordingly.