Effects of ammonia treatment on the morphologies of the catalytic metal films and carbon nanotubes subsequently synthesized via a thermal chemical vapor deposition method were investigated. An optimally controlled thermo-chemical process of ammonia treatment gave rise to a morphology of a dense distribution of vertically aligned carbon nanotubes. $NH_3$ treatment is a crucial key process to obtain vertically aligned carbon nanotubes. However, it was realized by a simple $NH_3$ treatment during synthesis at temperatures of $800-900^{circ}C$ without any extra process. The structure and morphology of carbon nanotubes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy.