Mems device and method for producing mems device

A method for producing a MEMS device, the method comprising:

• preparing a substrate having a first main surface and a second main surface opposite to the first main surface;
• forming a first trench extending from the first main surface toward the second main surface of the substrate;
• forming a vertical structure having a thermal expansion coefficient different from a thermal expansion coefficient of the substrate in the first trench by thermally oxidizing a wall surface of the first trench;
• forming a second trench extending from the first main surface toward the second main surface of the substrate through anisotropic etching to partition a movable electrode finger, a fixed electrode finger, and a beam portion in the substrate with the second trench, wherein the vertical structure is included in the beam portion;
• and
• forming a cavity by at least partially removing a portion of the substrate, which located on the second main surface side of the movable electrode finger, the fixed electrode finger, and the beam portion that have been partitioned, and forming the fixed electrode finger, the movable electrode finger, and the beam portion separated from a bottom surface of the cavity,
• wherein after the beam portion is separated from the bottom surface of the cavity, the beam portion deforms due to thermal stress generated in the beam portion due to a difference between thermal stress generated in a portion of the beam portion, the portion being adjacent to the vertical structure and thermal stress generated in the vertical structure, and an interval between the fixed electrode finger and the movable electrode finger becomes narrower due to deformation of the beam portion as compared with the interval formed before deformation of the beam portion.