Physical quantity sensor, physical quantity sensor device, and inertial measurement unit

A physical quantity sensor comprising:

• three axes orthogonal to each other being defined as an X axis, a Y axis, and a Z axis;
• a substrate;
• a first fixed electrode, a second fixed electrode, and a dummy electrode arranged to overlap the substrate in a plan view from a Z-axis direction along the Z-axis;
• and
• a movable body configured to swing with respect to the substrate about a rotation axis extending along the Y axis,
• the movable body including:
• a first surface and a second surface outwardly opposite to each other, the first surface facing the substrate;
• a first mass portion facing the first fixed electrode;
• and
• a second mass portion arranged across the rotation axis from the first mass portion and facing the second fixed electrode,
• the first mass portion including:
• a first region;
• and
• a second region farther from the rotation axis than the first region along the X axis, the first region and second region sharing a border wall therebetween, the border wall extending along the Z axis;
• and
• a step provided on the first, surface between the first region and the second region, and the step forming a boundary wall extending along the Z axis,
• wherein a first gap distance along the Z axis between the first fixed electrode and the first mass portion in the first region is smaller than a second gap distance along the Z axis between the first fixed electrode and the first mass portion in the second region,
• the second mass portion including:
• a third region;
• and
• a fourth region farther from the rotation axis than the third region along the X axis, the third and fourth regions sharing another border wall therebetween, the another border wall extending along the Z axis,
• a first through-hole group is provided in the first region, and a second through-hole group is provided in the second region,
• a third through-hole group is provided in the third region, and a fourth through-hole group is provided in the fourth region,
• the first fixed electrode is a first detection electrode configured to form a capacitance with the first mass portion,
• the second fixed electrode is a second detection electrode configured to form a capacitance with the second mass portion,
• the first detection electrode faces the first region and the second region of the first mass portion along the Z axis,
• the second detection electrode faces the third region and the fourth region of the second mass portion along the Z axis,
• an opening area of each of through-holes of the second through-hole group is larger than an opening area of each of through-holes of the first through-hole group,
• the movable body includes a torque generating section disposed on a side of the first mass portion opposite to a side of the second mass portion, and a fifth through-hole group is provided in the torque generating section,
• an opening area of each of through-holes of the fifth through-hole group is larger than each of the opening area of each of the through-holes of the first through-hole group and the opening area of each of the through-holes of the second through-hole group, and
• the torque generating section faces the dummy electrode.