The diffusion barrier properties of three different kinds of chemical vapor deposited (CVD) TiN films were compared against Cu. TiN(A) film (21 nm) was deposited by the thermal decomposition of a single source of tetrakis(dimethylamido)titanium at 400 degrees C. TiN(B) film (19 nm) was prepared by in situ N-2 plasma treatment after every 8 nm growth of TiN(A) film. Finally, TiN(C) film (28 nm) was deposited by the reaction of TiCl4 with NH3 at 630 degrees C. The densities of TiN(A), TiN(B), and TiN(C) films were 2.55, 4.04, and 4.17 g/cm(3), respectively. Both TiN(A) and TiN(B) films showed nanocrystalline microstructure with equiaxed grains, the sizes of which were about 4 and 7 nm, respectively. TiN(C) film showed a columnar grain structure with an average grain size of about 14 nm. Sheet resistance measurements, X-ray diffractometry analyses, and etch-pit test results consistently demonstrated that the barrier performances of TiN(A) and TiN(B) were superior to those of TiN(C). The diffusion barrier properties of CVD TiN films were discussed in view of the density and microstructure of the film.