A resonator using the MEMS technology is provided which improves the accuracy of a shape of electrodes so as avoid a short circuit that would otherwise be caused between input and output electrodes to thereby increase the reliability thereof. A resonator includes a substrate 101, an insulation layer 102 formed selectively on the substrate 101 as a sacrificial surface, a beam 103 formed on the substrate 101 via a space, a first support portion 104A formed on the insulation layer 102 of the same material as that of the beam 103, and electrodes formed with a space defined between the beam 103 and themselves for signals to be inputted thereinto and outputted therefrom. A sectional area of the beam 103 and a sectional area of the first support portion 104A are substantially equal in a section which is perpendicular to a longitudinal direction of the beam 103.