Inertia sensor and method of manufacturing the same

An inertia sensor, comprising:

• a first layer;
• and
• a third layer that is disposed over the first layer across a second layer,
• wherein the first layer has a first concave portion, a second concave portion, and a first convex portion between the first concave portion and the second concave portion,
• wherein the second layer has a first movable electrode, a second movable electrode, and a fixed portion between the first movable electrode and the second movable electrode,
• wherein the third layer has a third concave portion, a fourth concave portion, a second convex portion between the third concave portion and the fourth concave portion, a first fixed electrode, and a second fixed electrode,
• wherein the first movable electrode is disposed in a first cavity that is surrounded by the first concave portion and the third concave portion,
• wherein the second movable electrode is disposed in a second cavity that is surrounded by the second concave portion and the fourth concave portion,
• wherein the first fixed electrode is configured by a first portion of the third layer which is surrounded by a first through hole provided in the third layer, the first through hole being formed between a first inner wall surrounding the first fixed electrode and a first outer wall spaced from the first inner wall and surrounding the first inner wall,
• wherein the second fixed electrode is configured by a second portion of the third layer which is surrounded by a second through hole provided in the third layer, the second through hole being formed between a second inner wall surrounding the second fixed electrode and a second outer wall spaced from the second inner wall and surrounding the second inner wall,
• wherein at least one of (i) the first through hole has a portion in which the first outer wall is spaced from the first inner wall by a greater width to form a first wide portion or (ii) the second through hole has a portion in which the second outer wall is spaced from the second inner wall by another greater width to form a second wide portion, so as to form at least one wide portion,
• wherein the first inner wall and the first outer wall of the first through hole are covered with a first film, the first film covering the first inner wall has a first-film first-through-hole inner wall and the first film covering the first outer wall has a first-film first-through-hole outer wall, the first-film first-through-hole outer wall being spaced from the first-film first-through-hole inner wall by a first-film first-through-hole space,
• wherein the second inner wall and the second outer wall of the second through hole are covered with the first film, the first film covering the second inner wall has a first-film second-through-hole inner wall and the first film covering the second outer wall has a first-film second-through-hole outer wall, the first-film second-through-hole outer wall being spaced from the first-film second-through-hole inner wall by a first-film second-through-hole space, and
• wherein the first-film first-through-hole inner wall, the first-film first-through-hole outer wall, the first-film second-through-hole inner wall, and the first-film second-through-hole outer wall are covered by a second film, so as to fill (i) the first-film first-through-hole space between the first-film first-through-hole inner wall and the first-film first-through-hole outer wall and (ii) first-film second-through-hole space between the first-film second-through-hole inner wall and the first-film second-through-hole outer wall, except in the at least one wide portion where at least one gap is left open between the second film covering at least one of (i) the first-film first-through-hole inner wall and the second film covering the first-film first-through-hole outer wall at the first wide portion or (ii) the first-film second-through-hole inner wall and the second film covering the first-film second-through-hole outer wall at the second wide portion.