A semiconductor substrate has a front face with a first dielectric region. A capacitive element includes, on a surface of the first dielectric region at the front face, a stack of layers which include a first conductive region, a second conductive region and a third conductive region. The second conductive region is electrically insulated from the first conductive region by a second dielectric region. The second conductive region is further electrically insulated from the third conductive region by a third dielectric region. The first and third conductive regions form one plate of the capacitive element, and the second conductive region forms another plate of the capacitive element.