Some embodiments of the present disclosure provide a method of manufacturing a back side illuminated (BSI) image sensor. The method includes receiving a semiconductive substrate; forming a transistor coupled to a photosensitive element at a front side of the semiconductive substrate; forming a deep trench isolation (DTI) at a back side of the semiconductive substrate; forming a doped layer conformally over the DTI; performing a microwave anneal over the back side; forming a non-transparent material inside the DTI; and forming a color filter over the doped layer.