A method of forming a gate electrode in a semiconductor device which can easily perform etching process for forming the gate electrode and reduce the resistivity of a gate electrode, is disclosed. In the present invention, a gate oxide layer, an amorphous silicon layer and a tungsten silicide layer are sequentially formed on a semiconductor substrate. A mask oxide pattern is then formed on the tungsten silicide layer in the shape of a gate electrode. Next, the tungsten silicide layer and the amorphous silicon layer are etched using the mask oxide pattern as an etch mask, to form a gate electrode. Thereafter, the amorphous silicon layer and the tungsten silicide layer of the gate electrode are thermal-treated by RTP spike annealing and an oxide layer is then formed on the side wall of the gate electrode. According to the present invention, by reducing resistivity of a tungsten silicide layer, it is possible to apply a conventional gate electrode material to high integration device over 1GDRAM, thereby lowering cost to develop a new gate electrode material. Furthermore, etching process for forming a gate electrode is easily performed when using the tungsten silicide layer as the gate electrode material, thereby obtaining uniform gate electrode. As a result, the reliability of a device is improved.