In a method of manufacturing a semiconductor device, a first photoresist layer is applied on a polycrystalline silicon layer formed on a semiconductor substrate. The first photoresist layer is then patterned and cured with UV rays. The polycrystalline silicon layer is etched, using the first photoresist layer as a mask, to form a gate electrode and a resistive film of the polycrystalline silicon layer. A second photoresist layer is applied on the cured first photoresist layer and patterned to form an opening portion exposing the first photoresist layer. Impurities are ion implanted through the opening portion in the polycrystalline silicon layer. The channeling of impurities implanted during the ion implantation is suppressed by the cured first photoresist layer.