Image sensor including first and second overlapping device isolation patterns

1. An image sensor comprising:

a lower substrate including logic circuits;

an interconnection layer provided on the lower substrate, the interconnection layer electrically connected to the logic circuits;

an upper substrate provided on the interconnection layer, the upper substrate having pixels;

a first device isolation pattern provided in the upper substrate; and

a second device isolation pattern provided in the upper substrate,

wherein the upper substrate has a first surface and a second surface opposite to each other, the first surface so configured that light comes through the first surface into the image sensor,

wherein a combination of the first and second device isolation patterns penetrates the upper substrate from the first surface to the second surface,

wherein all transistors provided on the upper substrate are the same conductivity type,

wherein each of the transistors comprises:

source/drain regions provided in the upper substrate;

an upper gate electrode provided on the upper substrate; and

a silicon oxide layer disposed between the upper substrate and the upper gate electrode, the silicon oxide layer being in contact with the upper substrate and the upper gate electrode,

wherein the second device isolation pattern comprises a first part overlapping the first device isolation pattern in a plan view,

wherein the second device isolation pattern comprises a second part disposed between two transistors in a plan view, the two transistors disposed in one pixel of the pixels,

wherein depths of the first part and the second part of the second device isolation pattern in a perpendicular direction with respect to the first and second surfaces of the upper substrate are the same, and

wherein the first part and the second part of the second device isolation pattern comprise the same material.

2. The image sensor of claim 1 , wherein the silicon oxide layer does not include nitrogen.

3. The image sensor of claim 1 , wherein the source/drain regions include N-type dopants.

4. The image sensor of claim 1 , wherein the lower substrate comprises:

source/drain portions provided in the lower substrate;

a lower gate electrode provided on a channel region between the source/drain portions with respect to a plan view;

a silicon oxide pattern disposed between the lower substrate and the lower gate electrode; and

a silicon nitride pattern provided between the silicon oxide pattern and the lower gate electrode.

5. The image sensor of claim 4 , wherein a conductivity type of dopants included in the upper gate electrode is the same as that of dopants included in the lower gate electrode, and

wherein a silicon nitride layer is not provided between the upper substrate and the upper gate electrode.

6. The image sensor of claim 1 , wherein the upper gate electrodes of the transistors include a transfer gate electrode, a source follower gate electrode, a selection gate electrode, and a reset gate electrode.

7. The image sensor of claim 1 , wherein the first device isolation pattern defines the pixels; and

wherein the second device isolation pattern defines an active region in which the source/drain regions are formed.

8. The image sensor of claim 7 , wherein the second device isolation pattern is provided between the first device isolation pattern and the second surface of the upper substrate, wherein a sidewall of the second device isolation pattern is laterally offset from a sidewall of the first device isolation pattern.

9. The image sensor of claim 1 , further comprising:

a photoelectric conversion region provided in the upper substrate of each of the pixels;

a floating diffusion region disposed in the upper substrate of each of the pixels, the floating diffusion region disposed adjacent to the second surface of the upper substrate;

color filters disposed on the first surface of the upper substrate; and

micro lenses disposed on the color filters.

10. The image sensor of claim 1 , wherein the upper gate electrode includes dopants, and

wherein the dopants include arsenic (As) but do not include boron (B).

11. The image sensor of claim 1 , wherein the first device isolation pattern has a first surface coplanar with the first surface of the upper substrate and a second surface disposed opposite the first surface of the first device isolation pattern,

wherein an area of the first surface of the first device isolation pattern is greater than an area of the second surface of the first device isolation pattern.