Abstract: An improved quartz crystal resonator of the type comprising an AT type cut quartz plate is provided in which the plate comprises metallized main electrodes on opposed surfaces thereof which are surrounded by spaced apart metallized supplementary control electrodes. The opposed surfaces of the plate provide a non-metallized unused portion for the plate over a substantial portion of the opposed surfaces. Each of the supplementary control electrodes has at least an associated parameter of width, thickness, density, air gap distance from the respective main electrode and an applied electrode potential and each of the main electrodes has at least an associated corresponding parameter. At least one of the associated parameters of the supplementary electrodes is different from the corresponding associated parameter for the respective main electrodes for controlling the associated Q- factor and frequency of the spurious resonance frequencies.