To clarify the "epitaxial" fort-nation process of TiN films due to nitrogen-implantation, changes of crystallographic structures of as-deposited Ti films during N-implantation were studied by using a transmission electron microscope (TEM). Analysis of the results of TEM observations indicated that H atoms which constituted TiHx were completely released from as-deposited Ti films when the films were heated up to 350 degreesC, and that the H-released unstable fcc-Ti sublattice was transformed into hcp-structure. Ions of N-2(+) with 62 keV were implanted into the hcp-Ti films held at 350 degreesC. In the N-implanted Ti film (N/Ti = 0.954), there coexisted NaCl-type TiN, and a small amount of hcp-Ti. The (001)- and (110)-oriented TiNy were "epitaxially" formed by the transformation of (03.5)- and ((2) over bar1.0)-oriented hcp-Ti, respectively. The lattice of N-implanted hcp-Ti was expanded by the occupation of octahedral sites by N atoms. Strain due to the lattice expansion was considered as a driving force for the hcp-fcc transformation of Ti sublattice. (C) 2004 Elsevier B.V. All rights reserved.