Image sensor and method of forming the same

1. An image sensor comprising:

a substrate including a first surface opposing a second surface and a plurality of pixel regions, the second surface to receive incident light;

a photoelectric converter in each of the pixel regions;

a gate electrode on the photoelectric converter; and

a pixel isolation region isolating adjacent the pixel regions, wherein the pixel isolation region includes a first isolation layer coupled to a channel stop region, the first isolation layer includes a bottom surface adjacent to the second surface of the substrate and sidewalls extending toward the first surface of the substrate from the bottom surface of the first isolation layer,

wherein the channel stop region is an impurity-doped region, and

wherein the channel stop region is disposed between the bottom surface of the first isolation layer and the second surface of the substrate, and spaced apart from the sidewalls of the first isolation layer.

2. The image sensor as claimed in claim 1 , wherein:

the first isolation layer contacts the first surface; and

the channel stop region contacts the second surface.

3. The image sensor as claimed in claim 2 , further comprising:

a second isolation layer contacting the first surface, the second isolation layer being shallower than the first isolation layer.

4. The image sensor as claimed in claim 3 , wherein the first isolation layer and the second isolation layer are integrally formed as one body.

5. The image sensor as claimed in claim 1 , further comprising

an air gap region in the first isolation layer.

6. The image sensor as claimed in claim 1 , wherein a bottom surface or a top surface opposing to the bottom surface of the first isolation layer is uneven.

7. The image sensor as claimed in claim 1 , wherein:

the gate electrode is on the first surface, and

the image sensor further includes a color filter and a micro-lens on the second surface.

8. The image sensor as claimed in claim 1 , wherein:

the photoelectric converter includes dopants of a first conductivity type, and

the channel stop region includes dopants of a second conductivity type.

9. An image sensor, comprising:

a plurality of pixel regions, each pixel region including a photoelectric converter and an active region, the photoelectric converter being a first material doped with impurities of a first type, the photoelectric converter having a first surface on which light is incident and a second surface adjacent the active region; and

a first separator between adjacent pixel regions, and

a second separator disposed between adjacent the pixel regions and vertically overlapped with the first separator, wherein the first separator includes a first surface, co-planar with the first surface of the photoelectric converter, made of the first material doped with impurities of a second type, wherein the second separator contacts a second surface of the first separator opposing to the first surface of the first separator, and wherein the first separator is spaced apart from sidewalls of the second separator.

10. The image sensor as claimed in claim 9 , wherein a thickness of the first material doped with impurities of the second type is greater in a region in which only two pixel regions neighbor each other than in a region in which four pixel regions neighbor each other.

11. The image sensor as claimed in claim 9 , wherein the second separator extends from adjacent the active region to the first material doped with impurities of the second type.

12. The image sensor as claimed in claim 11 , wherein the second separator is wider adjacent the active region than adjacent the first material doped with impurities of the second type.

13. The image sensor as claimed in claim 11 , wherein the second separator includes an insulating layer and an air gap surrounded by the insulating layer.