This work reports on rapid-thermal-annealed TiN as a barrier for Pt/BST/Pt/TiN/Ti/Si capacitors. Experimental results indicate that the diffusion of Ti and Si from the Ti adhesion layer and Si plug, respectively, degrade the capacitor for the gigabit dynamic random access memories (DRAMs) using barium strontium titanate (BST) as a dielectric material. Although the diffusion barrier TiN between the bottom electrode Pt and Ti adhesion layer has been conventionally used to release the issue, the interdiffusion of Ti and Si occurs due to the thermal budget of the BST deposition. A rapid thermal annealing process is applied to the as-deposited TiN barrier against the interdiffusion. Excellent electrical characteristics, including high dielectric constant (εr = 320), low leakage current (1.5×10-8 A/cm2) under 0.1 MV/cm, and a lifetime greater than 10 years under 1.5 MV/cm are obtained. Our results further demonstrate that the proposed technique is highly promising for future high-density DRAMs.