In a method for forming a gate in a semiconductor device, a first preliminary gate structure is formed on a substrate. The first preliminary gate structure includes a gate oxide layer, a polysilicon layer pattern and a tungsten layer pattern sequentially stacked on the substrate. A primary oxidation process is performed using oxygen radicals at a first temperature for adjusting a thickness of the gate oxide layer to form a second preliminary gate structure having tungsten oxide. The tungsten oxide is reduced to a tungsten material using a gas containing hydrogen to form a gate structure. The tungsten oxide may not be formed on the gate structure so that generation of the whiskers may be suppressed. Thus, a short between adjacent wirings may not be generated.