The effect of substrate temperature and process pressure on microstructure of MOCVD-TiN films deposited on oxidized Si substrates are studied by transmission electron microscopy (TEM). It is found that microstructure of MOCVD-TiN films distinctly changes with these deposition parameters and that the resistivity of the films is uniquely related to the microstructure. Films with the lowest resistivity (< 500 μohm-cm) show a uniform semi-columnar grain structure. Films with the highest resistivity (> 10,000 μohm-cm) show a uniform equi-axed micrograin structure. The other films exhibit a bi-layer structure: one layer of semi-columnar grains and the other of equiaxed micrograins. The thickness ratio of these layers changes with the deposition conditions and the resistivity is a unique function of the thickness of the semi-columnar grain layer.