A method for fabricating a CMOS image sensor, comprising the following steps, in succession: forming a first dielectric layer on a first substrate; forming a plurality of discrete first electrodes on the first dielectric layer; forming a second dielectric layer to cover the first dielectric layer and the plurality of first electrodes; forming a plurality of etched trenches in the second dielectric layer with each etched trench exposing one or more surface portions of a corresponding first electrode; forming a first electrode material layer on sidewall and bottom surfaces of each etched trench to electrically connect to a corresponding first electrode, wherein preferably the plurality of first electrode material layers is made of doped polycrystalline silicon or a metal; forming a dielectric material layer to cover the second dielectric layer and the first electrode material layer in each etched trench; forming a second electrode material layer on the dielectric material layer to fill up each etched trench, the first electrode material layer and the second electrode material layer with the dielectric material layer therebetween forming a capacitor; forming a plurality of discrete second electrodes with each second electrode electrically connecting to a corresponding second electrode material layer and also covering corresponding portions of the dielectric material layer, wherein preferably the plurality of second electrode material layers is made of doped polycrystalline silicon or a metal; forming a plurality of discrete signal processing circuits on a second substrate; bonding the second substrate with the first substrate, wherein each signal processing circuit is electrically connected to a corresponding second electrode; removing the first substrate to expose the first dielectric layer; forming a plurality of discrete image sensing units on a third substrate; and bonding the third substrate with the exposed first dielectric layer, wherein each image sensing unit is electrically connected to a corresponding first electrode. forming a first dielectric layer on a first substrate; forming a plurality of discrete first electrodes on the first dielectric layer; forming a second dielectric layer to cover the first dielectric layer and the plurality of first electrodes; forming a plurality of etched trenches in the second dielectric layer with each etched trench exposing one or more surface portions of a corresponding first electrode; forming a first electrode material layer on sidewall and bottom surfaces of each etched trench to electrically connect to a corresponding first electrode, wherein preferably the plurality of first electrode material layers is made of doped polycrystalline silicon or a metal; forming a dielectric material layer to cover the second dielectric layer and the first electrode material layer in each etched trench; forming a second electrode material layer on the dielectric material layer to fill up each etched trench, the first electrode material layer and the second electrode material layer with the dielectric material layer therebetween forming a capacitor; forming a plurality of discrete second electrodes with each second electrode electrically connecting to a corresponding second electrode material layer and also covering corresponding portions of the dielectric material layer, wherein preferably the plurality of second electrode material layers is made of doped polycrystalline silicon or a metal; forming a plurality of discrete signal processing circuits on a second substrate; bonding the second substrate with the first substrate, wherein each signal processing circuit is electrically connected to a corresponding second electrode; removing the first substrate to expose the first dielectric layer; forming a plurality of discrete image sensing units on a third substrate; and bonding the third substrate with the exposed first dielectric layer, wherein each image sensing unit is electrically connected to a corresponding first electrode.