A micro-resistor includes a resistor material layer, an electrode set and a first protective layer. The electrode set includes a first electrode and a second electrode to define an opening which exposes the resistor material layer. A space between the first electrode and the second electrode represents an opening size. The first protective layer covers the opening completely and has a coverage size along a direction parallel with the space. The micro-resistor has a resistance of less than 5 milliohm and the difference of the opening size and the coverage size is less than 3100 micrometer to make the temperature coefficient of electrical resistance of the micro-resistor not greater than 150 ppm/° C.