Crystal resonator

A resonator comprising:

• a crystal substrate that has a first main surface and a second main surface that opposes the first main surface;
• first and second comb electrodes on the first main surface of the crystal substrate, each of the first and second comb electrodes including a plurality of electrode fingers that are alternately arranged and separated from each other,
• wherein the plurality of electrode fingers of the first comb electrode includes a first electrode finger and the plurality of electrode fingers of the second comb electrode includes a second electrode finger that is adjacent to the first electrode finger,
• wherein a thickness shear vibration is excited at a portion that overlaps with a gap between the first and second electrode fingers, which depends on a potential difference between the first and second electrode fingers, and
• wherein a duty ratio (L1+L2)/(2×P1) on a side of the first main surface is from 0.15 to 0.33 inclusive or from 0.62 to 0.82 inclusive, where L1 a width of the first electrode finger, L2 is a width of the second electrode finger, and P1 is a distance between the first and second electrode fingers in a direction in which the first and second electrode fingers extend.