By using a disc type resonator, a sensor detects a substance having a mass
and the mass with high sensitivity. Moreover, it is preferable to detect
a change in vibrations of a substance attached or adsorbed to an area
having a vibration amplitude equal to or larger than a constant value.
This disc type resonator can be fabricated by the MEMS technique by using
single-crystal or polycrystalline Si as a structural material. To improve
the attachment efficiency of molecules and the like to be detected,
irregularity or a groove is preferably provided on the surface of the
disc type resonator.