MEMS device, preparation method thereof and electronic device

The invention provides an MEMS device, a preparation method thereof and an electronic device, and the method comprises the steps: providing a substrate, and forming a sacrificial layer on the substrate; etching the sacrificial layer to expose part of the surface of the substrate; depositing a cavity covering material on an outer surface of the sacrificial layer, the cavity covering material covering a top surface and a side surface of the sacrificial layer; the cavity covering material is etched to form a release hole and at least one connecting groove, the release hole penetrates through the cavity covering material and exposes part of the sacrificial layer, the connecting groove is located on the outer side of the release hole, and the connecting groove extends into the cavity covering material from the surface of the cavity covering material; etching to remove at least part of the sacrificial layer through the release hole so as to form a cavity surrounded by the cavity covering material; and forming a rel