A method for manufacturing a capacitor of a semiconductor element including: forming a bottom electrode of the capacitor on a semiconductor substrate; performing rapid thermal nitrification (RTN) on the upper surface of the bottom electrode; performing a thermal process on the obtained structure having the bottom electrode in a furnace under a nitride atmosphere to eliminate stress generated by the RTN; forming Al2O3 and HfO2 dielectric films on the nitrified bottom electrode; and forming a plate electrode of the capacitor on the Al2O3 and HfO2 dielectric films. The thermal process is performed after the RTN performed on the surface of the bottom electrode, so that stress, generated from the RTN, is alleviated, thereby allowing the capacitor to obtain a high capacitance and lowering leakage current.