Semiconductor device and method of manufacturing the same

1. A semiconductor device comprising:

a substrate;

a first buffer layer formed over the substrate, wherein the first buffer layer contains hydrogen; and

an active layer formed on the first buffer layer and containing polycrystalline silicon and hydrogen,

wherein the concentration of the hydrogen contained in the active layer is about 1 atomic percent (at. %) or more, wherein the device further comprises a second buffer layer formed between and contacting the first buffer layer and the active layer, wherein the second buffer layer contains a smaller amount of hydrogen than the hydrogen in the first buffer layer and the hydrogen in the active layer,

wherein the first buffer layer comprises a first region and a second region located below the first region, and wherein the first region contains a greater amount of hydrogen than the second region,

wherein the active layer comprises a third region and a fourth region located on the third region, and wherein the third region contains a greater amount of hydrogen than the fourth region.

2. The semiconductor device of claim 1 , wherein the thickness of the second buffer layer is about 1000 Å or less.

3. The semiconductor device of claim 1 , further comprising a third buffer layer formed between the substrate and the first buffer layer.

4. The semiconductor device of claim 1 , wherein the first buffer layer comprises silicon nitride, and wherein the second buffer layer comprises silicon oxide.

5. The semiconductor device of claim 1 , wherein the active layer comprises a channel region and source and drain regions which are formed on both sides of the channel region and are doped with impurities, and wherein the semiconductor device further comprises;

a gate electrode formed on the active layer to at least partially overlap with the channel region;

an interlayer insulating layer formed on the substrate to cover the gate electrode and having contact holes which at least partially expose the source and drain regions;

source and drain electrodes filling the contact holes and formed on the interlayer insulating layer to be connected to the source and drain regions, respectively;

a passivation layer formed on the interlayer insulating layer to cover the source and drain electrodes;

a first electrode formed on the passivation layer and connected to at least one of the source and drain electrodes; and

a pixel defining layer formed on the passivation layer to expose the first electrode.

6. A semiconductor device comprising:

a substrate;

a first buffer layer formed over the substrate, wherein the first buffer layer contains hydrogen; and

an active layer formed on the first buffer layer and containing polycrystalline silicon and hydrogen,

wherein the concentration of the hydrogen contained in the active layer is about 1 atomic percent (at. %) or more, wherein the device further comprises a second buffer layer formed between and contacting the first buffer layer and the active layer, wherein the second buffer layer contains a smaller amount of hydrogen than the hydrogen in the first buffer layer and the hydrogen in the active layer,

wherein the semiconductor device further comprises:

a third buffer layer formed between the substrate and the first buffer layer, and

a fourth buffer layer formed between and contacting the third buffer layer and the substrate, wherein the fourth buffer layer contains hydrogen, and wherein the second and third buffer layers contain a smaller amount of hydrogen than the first and fourth buffer layers.

7. A method of manufacturing a semiconductor device, the method comprising:

forming a first silicon nitride layer over a substrate, wherein the first silicon nitride layer contains hydrogen;

forming a first silicon oxide layer on the first silicon nitride layer;

forming an amorphous silicon layer directly on the first silicon oxide layer, wherein the amorphous silicon layer contains hydrogen, and wherein the first silicon oxide layer contains a smaller amount of hydrogen than the hydrogen in the first silicon nitride layer and the hydrogen in the amorphous silicon layer; and

heat-treating the first silicon nitride layer, the first silicon oxide layer and the amorphous silicon layer so as to form a hydrogenated polycrystalline silicon layer,

wherein the forming of the first silicon nitride layer comprises:

forming a silicon oxide layer for a nitride layer on the substrate; and

injecting nitrogen into the silicon oxide layer for a nitride layer using a hydrogen-containing nitrogen source gas,

wherein the method further comprises:

forming a second silicon oxide layer between the substrate and the first silicon nitride layer; and

forming a second silicon nitride layer, containing hydrogen, between the substrate and the second silicon oxide layer to contact the second silicon oxide layer.

8. The method of claim 7 , wherein the second silicon oxide layer has a thickness of about 1000 Å or less.