AT-cut quartz crystal plates vibrating in the thickness-shear mode are well known as mass sensitive devices, also called quartz crystal microbalances (QCM). After deposition of a sensitive layer on one or both surfaces of the quartz discs these resonators are suitable for the application as chemical sensors for analysis in gaseous and liquid media. Up to now the resonant frequencies of these resonators are 5 to 30 MHz. The application of combined photolithographic and etching processes offers new promising approaches for the manufacturing of quartz resonators with higher resonant frequencies, up to 250 MHz, and smaller diameters, leading to higher sensitivities of the sensor device. So called inverted mesa resonators were fabricated and subsequently characterized optically, mechanically, and electrically. The measured Q-factors are about 5 104 , which is excellent for high frequency resonators. The correlation between electrode diameter and inharmonic modes was investigated. The influences of surface roughness and etch channels on the resonators' performance were examined. The behaviour under acoustic load was investigated experimentally. In liquid media, changes in the viscosity (?L) and density (pL) lead to a decrease of the resonant frequency (?f) of the QCM. A linear relationship between (?LPL)12 and ?f was observed, in agreement with theory, while the frequency shifts are much higher than reported before.