The Lame mode quartz crystal resonator vibrating in overtone mode is formed of an X-plate quartz crystal obtained in a manner that a blank X-plate quartz crystal having a coordinate of x, y and z axes is rotated through 36.5.degree. to 47.degree. about its y-axis and further rotated through 65.degree. to 85.degree. about a new x'-axis corresponding to the x-axis produced by the rotation about the y-axis and the thus rotated blank X-plate quartz crystal is then cut out along planes parallel to x-y, y-z and z-x planes of the original coordinate system, respectively. The quartz crystal resonator includes a vibrating portion, a supporting frame and a mounting portion formed integrally. The vibrating portion is connected through two connecting portions to the supporting frame and the mounting portion, as a result of which the quartz crystal resonator has less series resistance R.sub.1 and exhibits minimum vibrational energy losses and minimum frequency change over a wide temperature range.

An electronic thermometer has an oscillator, the frequency determining element of which is a temperature sensitive piezoelectric element, used as a measuring sensor, which is located in a sealed housing of electrically insulating material. The piezoelectric element is provided with two terminal electrodes, which are each connected via a respective capacitor to the oscillator circuit, and each of the two capacitors has electrodes, one located inside and one located outside the housing.

Quartz crystal resonators 30 with a first angle of rotation having an X-axis 17 and Z'-axis 19 lying within a plane corresponding to an AT-cut and a second angle of rotation 34 within the plane of the AT-cut and lying within a range of about .+-.1.degree. to about .+-.11.5.degree. from the Z'-axis of the AT-cut. The resonators includes substantially opposing electrodes 36 disposed on major faces of the quartz crystal plate 32. The second angle of rotation 34 results in quartz crystal resonators 30 being produced with a more uniform distribution of temperature performances.

A quartz oscillator temperature sensor which measures temperature based on the change in resonance or oscillation frequency of a quartz oscillator with the change in temperature of the oscillator can be constructed by cutting a piece of quartz from a wafer with a thickness of about 80 to 150 .mu.m by rotating the plane of the crystal defined by the electrical and mechanical axes 15 to 25.degree. about the electrical axis and then forming the wafer into a quartz tuning fork. The tuning fork is housed in a case sealed with a stem and coupled to electrical leads with heat resistent solder formed with more than about 90 wt % Pb and less than 10% Sn. The area within the case should be at a substantially high vacuum.

An apparatus for determining temperature of a semiconductor wafer during wafer fabrication is disclosed. The semiconductor wafer has a response circuit. The apparatus includes a signal transceiver for (i) transmitting an interrogation signal which excites the response circuit, and (ii) receiving a response signal generated by the response circuit. The apparatus also includes a processing unit electrically coupled to the signal transceiver. The apparatus also includes a memory device electrically coupled to the processing unit. The memory device has stored therein a plurality of instructions which, when executed by the processing unit, causes the processing unit to (a) operate the signal transceiver to (i) transmit the interrogation signal so as to excite the response circuit during fabrication of the semiconductor wafer, and (ii) measure the response signal generated by the response circuit, and (b) determine temperature of the semiconductor wafer based on the response signal of the response circuit.