An MEMS transducer is constituted of a diaphragm, a plate, a support structure for supporting the diaphragm and the plate with a gap layer surrounded by an interior wall, an electrode film (e.g. a pad conductive film) for covering a contact hole formed in the support structure, and a protective film (e.g. a pad protective film) which is formed on the support structure externally of the interior wall so as to cover the side surface of the electrode film having low chemical stability. The protective film is formed in the limited area including a part of the surface of the electrode film except for its center portion and the surrounding area of the electrode film. This allows the protective film to use materials having high membrane stress such as silicon nitride or silicon nitride oxide.