Abstract: MEMS device formed in a semiconductor body which is monolithic and has a first and a second main surface. A buried cavity extends into the semiconductor body below and at a distance from the first main surface. A diaphragm extends between the buried cavity and the first main surface of the semiconductor body and has a buried face facing the buried cavity. A diaphragm insulating layer extends on the buried face of the diaphragm and a lateral insulating region extends into the semiconductor body along a closed line, between the first main surface and the diaphragm insulating layer, above the buried cavity. The lateral insulating region laterally delimits the diaphragm and forms, with the diaphragm insulating layer, a diaphragm insulating region which delimits the diaphragm and electrically insulates it from the rest of the wafer.