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Describes the study of quartz temperature sensors based on new bulk acoustic wave microresonators operating in thickness modes. First, we compare the thermal sensitivity and the electromechanical coupling coefficients of singly or doubly rotated cuts. These investigations allow us to select some cuts with both a good thermal sensitivity and piezoelectric characteristics. In the second part, emphasis is placed on the micromachining of resonators suspended by four bridges. These two theoretical considerations lead to the choice of three cuts. Experimental measurements are then presented. The temperature-frequency characteristics of the resonators are measured over the range 20 to 100 /spl deg/C. Motional resistances and Q factors are determined at room temperature.