NOVELTY - The element (1) has a substrate (10) including a first principal surface and a second principal surface respectively forming an obverse surface and a reverse surface of the substrate and vibrating in thickness-shear vibration mode. A first excitation electrode (25a) is formed on the first principal surface, and includes a side with an internal contact with imaginary quadrangle. A second excitation electrode (25b) is formed on the second principal surface, where relationship is satisfied by using parameters e.g. area of quadrangle and area of first excitation electrode.    USE - Resonator element for use in a resonator i.e. AT-cut quartz crystal resonator, of an electronic device such as voltage controlled oscillator and temperature compensated oscillator, an electronic apparatus such as mobile type or laptop type personal computer, cellular phone and digital still camera, mobile object (all claimed) such as hybrid car or electric car, and an electronic control unit. Uses include but are not limited to keyless entry system, immobilizer, car navigation system, car air-conditioner, anti-lock braking system (ABS), air-bag system, tire pressure monitoring system (TPMS), engine controller, battery monitor for hybrid car or electric car, or vehicle posture control system.    ADVANTAGE - The excitation electrodes are formed using a metal mask method when area of overlapping portions of the first excitation electrode and the second excitation electrode hardly varies even when displacement between the masks occurs, so that small variation of capacitance ratio can be obtained, a voltage controlled oscillator having high pulling sensitivity can be obtained, and ohmic loss of an electrode film can be reduced to reduce deterioration of capacitance value. The element includes a lead electrode to extend from an outer edge of a part of the first excitation electrode other than a cut-out part, so that the lead electrode can be prevented from passing in the area effective for decreasing the capacitance ratio by making the lead electrode extend from the outer edge of the part of the first excitation electrode. The element is excited with fundamental wave when the capacitance ratio is low, so that the voltage controlled oscillator with a broader pull range and noise ratio can be obtained, and the oscillator with frequency reproducibility, aging characteristic and frequency-temperature characteristic can be formed.    DETAILED DESCRIPTION - The substrate is a quartz crystal substrate i.e. AT-cut quartz crystal substrate. INDEPENDENT CLAIMS are also included for the following:    (1) a resonator    (2) an electronic device    (3) an electronic apparatus    (4) a mobile object.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of a resonator element.    Resonator element (1)    Substrate (10)    Thick-wall sections (13-16)    Thick-wall main bodies (14a, 15a, 16a)    Excitation electrodes (25a, 25b)