Abstract: The invention relates to a variable-capacitance electrical capacitor comprising a first electrode and a second electrode facing the first electrode and a zone of a dielectric material arranged between said first and second electrodes characterized in that the second electrode is formed at least on one hand of a primary electrode made of an electrically conductive material and, at least on the other, of an additional electrode comprising a state-change material, the primary electrode and the additional electrode facing the first electrode, said state-change material being arranged at least partially in contact with the primary electrode and configured to alternatively adopt a high-resistivity state wherein the additional electrode is electrically insulated from the primary electrode and a low-resistivity state wherein the additional electrode is in electrical conduction with the primary electrode so as to vary the electrically active surface area of the second electrode.