A CMOS image sensor and a method of fabricating the same are provided. The CMOS image sensor includes: a semiconductor substrate of a first conductivity type having a photodiode region and a transistor region defined therein; a gate electrode formed above the transistor region of the semiconductor substrate with a gate insulating layer interposed therebetween; a first impurity region formed of the first conductivity type in the semiconductor substrate below the gate electrode and having a higher concentration of first conductivity type ions than the semiconductor substrate; and a second impurity region formed of a second conductivity type in the photodiode region of the semiconductor substrate.