This disclosure provides implementations of methods, apparatus and systems for producing acoustic wave devices and for selectively modifying one or more acoustic or electromechanical characteristics of such devices. In one aspect, a method includes depositing a structural layer over a substrate. The structural layer includes a plurality of structural portions, each being positioned over a corresponding device region. The method also includes arranging a mask layer over the structural layer. The mask layer includes a plurality of mask portions, each including a number of mask openings that expose a corresponding region of the structural portion. The method also includes accelerating dopant particles toward the mask layer. The accelerated dopant particles that proceed through the mask openings are impacted into the corresponding structural portion. The impacted dopant particles modify material properties in the structural portion, which then effect a change in the acoustic or electromechanical characteristics of the acoustic wave device.