Acceleration sensor with ring-shaped movable electrode

An acceleration sensor comprising:

• a substrate having a substrate surface;
• an anchor part fixedly disposed on the substrate surface;
• a movable electrode suspending above the substrate;
• a beam connecting the anchor part and the movable electrode and is elastically deformed by an acceleration produced in a parallel direction parallel to the substrate surface to displace the movable electrode in the parallel direction;
• a fixed electrode fixedly disposed on the substrate surface, for contacting the movable electrode, when the movable electrode is displaced by the acceleration, to detect the acceleration;
• and
• contacting state keeping means for keeping the movable electrode in contact with the fixed electrode after the acceleration disappears.

An acceleration sensor comprising:

• a substrate;
• an anchor part fixedly disposed on the substrate a movable electrode disposed over the substrate and having a cylindrical movable electrode side face;
• a beam connecting the anchor part and the movable electrode and elastically deformed to displace the movable electrode in a first direction approximately parallel to a surface of the substrate by acceleration applied in the direction;
• a deformation preventing film provided on the beam on an opposite side of the substrate to apply a force to the beam in a second direction opposite to a gravitational direction approximately perpendicular to the first direction;
• and
• a fixed electrode fixedly disposed on the substrate and having a cylindrical fixed electrode side face that makes a specific interval with the movable electrode side face when no acceleration is applied to the movable electrode,
• wherein the acceleration is detected based on a change in interval between the movable electrode side face and the fixed electrode side face;
• and
• wherein a length of the beam in the first direction is smaller than a thickness of the beam in the gravitational direction.

An acceleration sensor comprising:

• a substrate;
• an anchor part fixedly disposed on the substrate;
• a movable electrode disposed over the substrate and having a cylindrical movable electrode side face;
• a beam connecting the anchor part and the movable electrode and elastically deformed to displace the movable electrode in a direction approximately parallel to a surface of the substrate by acceleration applied in the direction;
• and
• a fixed electrode fixedly disposed on the substrate and having a cylindrical fixed electrode side face that makes a specific interval with the movable electrode side face when no acceleration is applied to the movable electrode,
• wherein the acceleration is detected based on a change in interval between the movable electrode side face and the fixed electrode side face;
• wherein a thickness of the movable electrode is thinner than that of the anchor part;
• and
• wherein surfaces of the anchor part, the beam, and the movable electrode on an opposite side of the substrate are on a plane in a state where no gravitational force is applied to the movable electrode and the beam.