The invention provides a back-illuminated
CMOS image sensor and a manufacturing method thereof. The structure such as a bonding pad can be formed through the application of four photomasks, so that the application of the photomasks is reduced; and furthermore, a formed
metal gridding is connected with the bonding pad, and comprises a first
metal wire positioned in a first isolation groove, a second
metal wire positioned in a second isolation groove, and a third metal wire for connecting the bonding pad, the first metal wire and the second metal wire, so that incident light can be preferably limited through the metal gridding, the appearance of
crosstalk is avoided, and the quality of the back-illuminated
CMOS image sensor is improved. Further, negative pressure is applied onto the bonding pad, so that the negative pressure is also applied onto the metal gridding connected with the bonding pad, namely the negative pressure is applied on a first isolation structure formed in the first isolation groove and a second isolation structure formed in the second isolation groove, and the generation of noisy points and
dark current can be inhibited through the negative pressure applied onto the first isolation structure and the second isolation structure.