A method of manufacturing a resistor is provided. At first, a semiconductor layer including at least a high resistance region and a low resistance region is formed on a substrate. Following that, a first ion implantation process is performed to the entire surface of the semiconductor layer, and a second ion implantation process is performed to the portions of the semiconductor layer within a predetermined region, so that the semiconductor layer has a higher doping concentration within the predetermined region than in the other regions. Therein, the predetermined region overlaps the low resistance region, the junction between the low resistance region and the high resistance region, and the portions of the high resistance region adjacent to the junction between the low resistance region and the high resistance region.