Tungsten etchback process was investigated for 0.45${mu}$m contacts using S$F_6$ high density plasma. Etch rates of tungsten and TiN were presented as a function of source power, bias power, and pressure. Tungsten etch rate increased with source power and pressure but was independent of bias power. In the case of TiN, the etch rate increased with bias power, which revealed that etching characteristic of TiN was more physical than that of tungsten. Optical Enission Spectroscopu(OES) method was used to measure and analyze emission intensities of gas phase species i.e., F, S, and W atom during etching process. In tungsten plug teching, depemdencies of plug loss rate on source power and pressure were same with the results of etch rate of blanket tungsten etching. In the case of bias power dependence, plug loss rate in tungsten plug etching increased with bias power, however, etch rate in blanket tungsten etching decreased with bias power it is considered that this discrepancy originated from redeposition of etching by-products such as Ti$F_X$ and Ti$N_X$$F_X$ and its temperature dependence.