Method for manufacturing CMOS image sensor

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Reference will now be made in detail to embodiments of the invention, examples of which are illustrated in the accompanying drawings.
Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
FIG.
2a illustrates a top view of a CMOS image sensor 100 consistent with an embodiment of the present invention and FIG.
2b shows a partial cross-sectional view of CMOS image sensor 100 along line 2 2' of FIG.
2a.
As shown in FIG.
2a, image sensor 100 includes a plurality of transistors 102, e.
g.
, 102-1, 102-2, 102-3, and a photodiode (not numbered) formed in a pixel region 104.
Each transistor 102 includes a gate electrode 106 and source/drain regions 108, as shown in FIG.
2a.
Also shown in FIG.
2a is an active region 110 defined between transistor 102-1 and pixel region 104.
In the exemplary configuration of CMOS image sensor 100 as shown in FIG.
2a, transistor 102-2 is a drive transistor and active region 110 is connected to gate electrode 106 of transistor 102-2.
In one aspect, gate electrodes 106 of transistors 102 comprise polysilicon and active region 110 is covered by horizontally extending the polysilicon of gate electrode 106 of transistor 102-2, as shown in FIG.
2a.
A salicide process may then be performed to connect the extended polysilicon to active region 110.
Consequently, a later metallic interconnect process only needs to form one single contact 112 on gate electrode 106 of transistor 102-2, as shown in FIG.
2b, in contrast to two first metal contacts 20-A and 20-B on both active region 18 and gate electrode 16-2 as required by the prior art, as shown in FIGS.
1a and 1b.
FIGS.
3a 3f are top views illustrating an exemplary process for manufacturing image sensor 100 consistent with an embodiment of the present invention.
FIGS.
4a 4f illustrate corresponding cross-sectional views of image sensor 100 during the manufacturing process along lines A A' as shown in FIGS.
3a 3f.
Referring to FIGS