In a method for forming a gate electrode, a dielectric layer having a high dielectric constant is formed on a substrate. Tantalum amine derivatives represented by a chemical formula Ta(NR.sub.1)(NR.sub.2R.sub.3).sub.3 in which R.sub.1, R.sub.2 and R.sub.3 represent H or C.sub.1 C.sub.6 alkyl group are introduced onto the dielectric layer to form a tantalum nitride layer. A capacitor metal layer or a gate metal layer is formed on the tantalum nitride layer. The capacitor metal layer or the gate metal layer and the tantalum nitride layer are patterned to form a capacitor electrode or a gate electrode. The tantalum amine derivatives are used in forming a dual gate electrode.