Thin film transistors having ldd regions

Claim 2

A semiconductor device comprising: a pixel portion and a driver circuit for the pixel portion on a same substrate; a first n-channel thin film transistor being formed in the pixel portion and including: a first active layer; at least a first LDD region in the first active layer; a first gate insulating film being formed between the first active layer and the substrate; a first gate electrode being formed between the first gate insulating film and the substrate; a second n-channel thin film transistor being formed in the driver circuit and including: a second active layer; at least a second LDD region in the second active layer; a second gate insulating film being formed between the second active layer and the substrate; a second gate electrode being formed between the second gate insulating film and the substrate, wherein the first LDD region of the first n-channel thin film transistor in the pixel portion is not overlapped with the first gate electrode, wherein the second LDD region of the second n-channel thin film transistor in the driver circuit is overlapped with the second gate electrode, wherein the first LDD region includes an n-type impurity at a first concentration while the second LDD region includes the n-type impurity at a second concentration, wherein the second concentration is higher than the first concentration.

Claim 3

A device according to claim 1 , wherein the second concentration is two or more times higher than the first concentration while the second concentration does not exceed ten times the first concentration.

Claim 4

A device according to claim 1 further comprising: an organic resin film being formed on at least the first n-channel thin film transistor in the pixel portion; a light shielding film being formed on the organic resin film; a dielectric film being formed in contact with the light shielding film; a pixel electrode being connected to the first n-channel thin film transistor in the pixel portion, a portion of said pixel electrode being overlapped with the light shielding film; wherein a capacitor is formed of the light shielding film, a dielectric film and the portion of the pixel electrode.

Claim 5

A device according to claim 3 , wherein the light shielding film comprises at least a material selected from the group consisting of aluminum, tantalum and titanium, and wherein the dielectric film comprises an oxide of the material.

Claim 6

A device according to claim 1 , wherein the semiconductor device includes one selected from the group consisting of a cellular phone, a video camera, a mobile computer, a goggle type display, a projector, a portable electronic book, a digital camera, a navigation system for vehicles, and a personal computer.

Claim 9

A method according to claim 6 , wherein the second concentration is two or more times higher than the first concentration while the second concentration does not exceed ten times the first concentration.

Claim 10

A method according to claim 6 further comprising the steps of: forming an organic resin film on at least the first n-channel thin film transistor in the pixel portion; forming a light shielding film on the organic resin film; forming a dielectric film in contact with the light shielding film; forming a pixel electrode being connected to the first n-channel thin film transistor in the pixel portion, a portion of said pixel electrode being overlapped with the light shielding film; wherein a capacitor is formed of the light shielding film, a dielectric film and the portion of the pixel electrode.

Claim 11

A method according to claim 8 , wherein the light shielding film comprises at least a material selected from the group consisting of aluminum, tantalum and titanium, and wherein the dielectric film comprises an oxide of the material.

Claim 12

A method according to claim 9 , wherein the dielectric film is formed through an anodic oxidation method.

Claim 13

A method according to claim 6 , wherein the semiconductor device includes one selected from the group consisting of a cellular phone, a video camera, a mobile computer, a goggle type display, a projector, a portable electronic book, a digital camera, a navigation system for vehicles, and a personal computer.

Claim 14

A semiconductor device comprising: a pixel portion and a driver circuit for the pixel portion on a same substrate; a first bottom gate type n-channel thin film transistor being formed in the pixel portion and including: a first gate electrode on an insulating surface; a first semiconductor island being formed over the first gate electrode having a first gate insulating film interposed therebetween, said first semiconductor island including a first source region, a first drain region, a first channel region, and a pair of first lightly doped drain (LDD) regions; at least a CMOS circuit being formed in the driver circuit and including a second bottom gate type n-channel thin film transistor and a bottom gate type p-channel thin film transistor; said second bottom gate type n-channel thin film transistor including: a second gate electrode on the insulating surface; a second semiconductor island being formed over the second gate electrode having a second gate insulating film interposed therebetween, said second semiconductor island including a second source region, a second drain region, a second channel region, and a pair of second LDD regions; said bottom gate type p-channel thin film transistor including: a third gate electrode being formed on the insulating surface; a third semiconductor island being formed over the third gate electrode having a third gate insulating film interposed therebetween, said third semiconductor island including a third source region, a third drain region, and a third channel region, wherein each of the first LDD regions of the first bottom gate type n-channel thin film transistor in the pixel portion is not overlapped with the first gate electrode, wherein each of the second LDD regions of the second bottom gate type n-channel thin film transistor in the driver circuit is overlapped with the second gate electrode, wherein each of the first LDD regions includes an n-type impurity at a first concentration while each of the second LDD regions includes the n-type impurity at a second concentration, wherein the second concentration is higher than the first concentration.

Claim 15

A semiconductor device comprising: a pixel portion and a driver circuit for the pixel portion on a same substrate; a first bottom gate type n-channel thin film transistor being formed in the pixel portion and including: a first gate electrode on an insulating surface; a first semiconductor island being formed over the first gate electrode having a first gate insulating film interposed therebetween, said first semiconductor island including a first source region, a first drain region, a first channel region, and a pair of first lightly doped drain (LDD) regions; at least a CMOS circuit being formed in the driver circuit and including a second bottom gate type n-channel thin film transistor and a bottom gate type p-channel thin film transistor; said second bottom gate type n-channel thin film transistor including: a second gate electrode on the insulating surface; a second semiconductor island being formed over the second gate electrode having a second gate insulating film interposed therebetween, said second semiconductor island including a second source region, a second drain region, a second channel region, and a pair of second LDD regions; said bottom gate type p-channel thin film transistor including: a third gate electrode being formed on the insulating surface; a third semiconductor island being formed over the third gate electrode having a third gate insulating film interposed therebetween, said third semiconductor island including a third source region, a third drain region, and a third channel region, wherein each of the first LDD regions of the first bottom gate type n-channel thin film transistor in the pixel portion is not overlapped with the first gate electrode, wherein each of the second LDD regions of the second bottom gate type n-channel thin film transistor in the driver circuit is overlapped with the second gate electrode, wherein each of the first LDD regions includes an n-type impurity at a first concentration while each of the second LDD regions includes the n-type impurity at a second concentration, wherein the second concentration is higher than the first concentration.

Claim 16

A device according to claim 12 , wherein the second concentration is two or more times higher than the first concentration while the second concentration does not exceed ten times the first concentration.

Claim 17

A device according to claim 12 further comprising: an organic resin film being formed on at least the first bottom gate type n-channel thin film transistor in the pixel portion; a light shielding film being formed on the organic resin film; a dielectric film being formed in contact with the light shielding film; a pixel electrode being connected to the first bottom gate type n-channel thin film transistor in the pixel portion, a portion of said pixel electrode being overlapped with the light shielding film; wherein a capacitor is formed of the light shielding film, a dielectric film and the portion of the pixel electrode.

Claim 18

A device according to claim 14 , wherein the light shielding film comprises at least a material selected from the group consisting of aluminum, tantalum and titanium, and wherein the dielectric film comprises an oxide of the material.

Claim 19

A device according to claim 12 , wherein the semiconductor device includes one selected from the group consisting of a cellular phone, a video camera, a mobile computer, a goggle type display, a projector, a portable electronic book, a digital camera, a navigation system for vehicles, and a personal computer.

Claim 20

A device according to claim 12 , wherein the organic resin film comprises at least a material selected from the group consisting of polyimide, acrylic resin, polyamide, polyimideamide, BCB (benzocyclobutene).

Claim 21

A device according to claim 12 , wherein each of the second LDD regions has a length in a range of 0.5-3.0 μm, preferably 1.0 to 1.5 μm, in a channel length direction while each of the first LDD regions has a length in a range of 0.5 to 3.5 μm, typically 1.5 to 2.5 μm in the channel length direction.

Claim 22

A device according to claim 13 , wherein the first concentration is in a range of 1×10 17 to 2.5×10 18 cm −3 , while the second concentration is in a range of 2×10 17 to 5×10 18 cm −3 .

Claim 23

A device according to claim 12 , wherein the n-type impurity comprises phosphorus.