Detection device, preparation method thereof and sensing device

The invention provides a detection device, a preparation method thereof and a sensing device, and relates to the field of micro electro mechanical systems, the detection device comprises a substrate, a sensing film and a cavity structure, and the cavity structure is located between the substrate and the sensing film; one of the substrate and the sensing film is provided with a release hole, an expansion layer is arranged in the release hole and covers the side wall of the release hole, the film layer where the release hole is located comprises a first surface and a second surface which are oppositely arranged, the first surface is arranged close to the cavity structure, and the second surface is arranged close to the cavity structure. The expansion layer extends from the interior of the release hole to at least partial area of the first surface and at least partial area of the second surface; wherein the expansion layer is configured to be capable of closing the release hole or reducing the hole diameter of t