Patent ID: 8039922

Claim:
A variable capacitor comprising: a support substrate; a first electrode formed as a thin film on a surface of the support substrate; a flat plate shaped second electrode provided in a fixed position above the first electrode and provided with a plurality of comb teeth portions projecting out toward the first electrode; a flat plate shaped third electrode disposed between the first electrode and the second electrode, the third electrode retained so as to be movable with respect to the second electrode in a vertical direction and a horizontal direction, provided with a plurality of comb teeth portions facing toward spaces between the plurality of comb teeth portions of the second electrode and projecting out toward the second electrode, with the surface of the third electrode covered in a dielectric layer, wherein a variable capacitor is configured by the third electrode and the second electrode, and the third electrode moves in a vertical direction according to a first voltage applied between the first electrode and the second electrode; a flat plate shaped fourth electrode disposed in a fixed position above the first electrode, the fourth electrode being connected in the horizontal direction to the second electrode, provided with a plurality of comb teeth portions projecting out toward the first electrode, and being electrically insulated from the second electrode; a flat plate shaped fifth electrode disposed between the first electrode and the fourth electrode, the fifth electrode being connected in a horizontal direction to the third electrode and provided with at least one comb tooth portion facing toward a space between the plurality of comb teeth portions of the fourth electrode and projecting out toward the fourth electrode, the surface of the fifth electrode being covered in a dielectric layer, the fifth electrode configuring with the fourth electrode a vibration prevention portion that prevents vibration of the third electrode, the fifth electrode moving in a horizontal direction according to a second voltage applied between the fourth electrode and the fifth electrode with the comb teeth portions of the fourth electrode and the comb teeth portion(s) of the fifth electrode making contact and fixing the fifth electrode to the fourth electrode due to frictional force.