A variety of techniques may be employed, alone or in combination, to enhance contact between a processed substrate and applied megasonic energy. In accordance with one embodiment of the new invention, the vibration plate is brought into intimate contact with one surface of the substrate, while cleaning or processing fluid contacts the other. In accordance with an alternative embodiment of the present invention, a reflecting surface may be provided to cause emanated energy to be reflected back into the near field and make it more uniform. In accordance with another alternative embodiment of the present invention, energy may be transferred across a substrate bounded on both sides by liquid with incidence of megasonic energy that is either normal to the substrate surface or within a critical range of incident angles. In yet another embodiment, generated dilatational waves may be converted to surface waves prior to contacting the substrate.