Ru and RuO2 thin films were grown on Si, SiO2 and TiN substrates by pulsed chemical vapor deposition using RuO4 and 5%H2/95%N2 as the precursor and reducing gas, respectively. Ru film showed an excellent thermal stability, high growth rate of 0.18nm/pulse (0.43nm/min), low impurity concentration, conformal step coverage and very smooth surface. The TiO2 film grown on this Ru electrode showed much improved electrical performance compared to those on the other Ru electrode. RuO2 thin film can be deposited by decreasing the H2/N2 gas supply rate. RuO2 thin film has excellent conformal step coverage on a hole structure with an opening diameter of 100nm and a depth of 1000nm. With ¬RuO2 thin film as sub-electrode of MIM capacitor, the equivalent oxide thickness of TiO2 film could be decreased to 0.56nm within the specification of DRAM leakage current.