A method for manufacturing a CMOS image sensor includes: preparing a semiconductor substrate incorporating therein a p-type epitaxial layer by epitaxially growing up an upper portion of the semiconductor substrate; forming a pixel array in one predetermined location of the semiconductor substrate, the pixel array having a plurality of transistors and a photodiode therein, wherein each transistor employs a gate insulator with a thickness ranging from 40 Å to 90 Å; and forming a logic circuit in the other predetermined location of the semiconductor substrate, the logic circuit having at least one transistor, wherein the transistor employs a gate insulator with a thickness ranging from 5 Å to 40 Å.