place substantially at the center of pad 3 to symmetrically expose separate portions of its upper surface a second conductive layer 7 is formed on the walls and the bottom of each opening layer 7 results for example from a conformal deposition of polysilicon followed by a chem mech etching of the portion of the polysilicon deposition covering the upper surface of layer 4 a first capacitor electrode 7 in electric contact with an underlying substrate 1 formed of two independent half electrodes 7 1 and 7 2 has thus been formed as previously each of half electrodes 7 1 and 7 2 is substantially cup shaped the bottom of each half electrode 7 1 7 2 has thus in cross section view fig3 a a recess 8 1 8 2 that follows the contour of a portion of pad 3 protruding from insulating layer 2 each of half electrodes 7 1 and 7 2 has in top view fig3 b substantially the shape of a rectangle it should be noted that the surface of each of half electrodes 7 1 and 7 2 is greater than half the surface of a conventional electrode such as illustrated in fig1 a and 1b.