a capacitor in a semiconductor integrated circuit is fabricated having a fixed charge density introduced near an electrode / dielectric interface . the fixed charge density compensates for the effects of a depletion layer , which would otherwise lower the effective capacitance . by shifting the undesirable effect of the depletion capacitance outside of the operating voltage range , the capacitor is effectively converted to an accumulation mode . the fixed charge density is preferably introduced by a plasma nitridation process performed prior to formation of the capacitor dielectric .