Methods of manufacturing thin film transistors using masks to protect the channel regions from impurities while doping a semiconductor layer to form source/drain regions

1. A method of manufacturing a thin film transistor, comprising:

forming a semiconductor layer on a substrate;

forming a gate insulating layer over an entire surface of the substrate to cover the semiconductor layer;

depositing a conductive layer on the gate insulating layer;

forming a photosensitive pattern having a thickness of at least 5,000 Å over the conductive layer;

patterning the conductive layer according to the photosensitive pattern to form a gate electrode; and

ion-doping a p + -type impurity into the semiconductor layer using the photosensitive pattern as a mask to form source and drain regions;

wherein a hydrogen ion density is constant according to a depth of the semiconductor layer in a channel region of the semiconductor layer.

2. The method according to claim 1 , wherein the thin film transistor is a p-type thin film transistor.

3. The method according to claim 1 , wherein the thin film transistor is a CMOS transistor.

4. A method of manufacturing a thin film transistor, comprising:

forming a semiconductor layer on a substrate;

forming a gate insulating layer over an entire surface of the substrate to cover the semiconductor layer;

depositing a conductive layer on the gate insulating layer;

forming a photosensitive pattern on a portion of the conductive layer corresponding to the semiconductor layer;

patterning the conductive layer according to the photosensitive pattern to form a gate electrode;

removing the photosensitive pattern;

forming an impurity shielding layer on the gate electrode, the impurity shielding layer being made of a metal layer; and

ion-doping an impurity into the semiconductor layer using the impurity shielding layer as a mask to form source and drain regions;

wherein a hydrogen ion density is constant according to a depth of the semiconductor layer in a channel region of the semiconductor layer.

5. The method according to claim 4 , wherein the metal layer is made of one of Mo, W, MoW, Al, and AlNd.

6. The method according to claim 5 , wherein the impurity shielding layer has one or more layers.