Thin films of titanium nitride are prepared on metallic substrates using rf reactive sputtering. A pure titanium target and argon plasma are used with reactive gas of nitrogen in the sputter. The pressure of Ar is 0.53 Pa, and the input power 300 W. The reactive gas is periodically added to a constant plasma supporting Ar flow as a form of square waves, and this is called the modulation method. Wide atomic ratios of N to Ti, 0.3 to unity, are obtained by changing the duty ratio or period, where the stoichiometric ratio of TiN is unity. The variation of the atomic ratio is slower than that of the continuous nitrogen gas addition and this promises easy handling for producing a film with a particular atomic ratio. Moreover, the deposition rates are maintained within a factor of 30% decrease. These results indicate possible application to bulky material preparations such as functionally gradient materials (FGMs) and FGM-like intermediate layers for composite materials.