Method of fabricating a semiconductor device
First Claim
1. An electronic equipment having a display device comprising:
- a substrate;
a first thin film transistor formed over the substrate, said first thin film transistor comprising;
a first semiconductor island including at least a first channel formation region, a second channel formation region, lightly doped regions and source and drain regions;
a first gate insulating film formed over the first semiconductor island;
a first gate electrode formed over the first channel formation region with the first gate insulating film interposed therebetween; and
a second gate electrode formed over the second channel formation region with the first gate insulating film interposed therebetween;
a driving circuit including at least one second thin film transistor formed over the substrate, said second thin film transistor comprising;
a second semiconductor island including at least a third channel formation region;
a second gate insulating film formed over the second semiconductor island;
a third gate electrode formed over the third channel formation region with the second gate insulating film interposed therebetween;
an interlayer insulating film covering the first, second and third gate electrodes and said first and second semiconductor islands; and
a pixel electrode formed over the interlayer insulating film and electrically connected to one of the source and drain regions of the first semiconductor island, wherein each of the first, second and third gate electrodes has tapered edges with a taper angle in a range of 3°
to 60°
.
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Abstract
There is provided a thin film transistor having improved reliability. A gate electrode includes a first gate electrode having a taper portion and a second gate electrode with a width narrower than the first gate electrode. A semiconductor layer is doped with phosphorus of a low concentration through the first gate electrode. In the semiconductor layer, two kinds of n−-type impurity regions are formed between a channel formation region and n+-type impurity regions. Some of the n−-type impurity regions overlap with a gate electrode, and the other n−-type impurity regions do not overlap with the gate electrode. Since the two kinds of n−-type impurity regions are formed, an off current can be reduced, and deterioration of characteristics can be suppressed.
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Citations
45 Claims
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1. An electronic equipment having a display device comprising:
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a substrate;
a first thin film transistor formed over the substrate, said first thin film transistor comprising;
a first semiconductor island including at least a first channel formation region, a second channel formation region, lightly doped regions and source and drain regions;
a first gate insulating film formed over the first semiconductor island;
a first gate electrode formed over the first channel formation region with the first gate insulating film interposed therebetween; and
a second gate electrode formed over the second channel formation region with the first gate insulating film interposed therebetween;
a driving circuit including at least one second thin film transistor formed over the substrate, said second thin film transistor comprising;
a second semiconductor island including at least a third channel formation region;
a second gate insulating film formed over the second semiconductor island;
a third gate electrode formed over the third channel formation region with the second gate insulating film interposed therebetween;
an interlayer insulating film covering the first, second and third gate electrodes and said first and second semiconductor islands; and
a pixel electrode formed over the interlayer insulating film and electrically connected to one of the source and drain regions of the first semiconductor island, wherein each of the first, second and third gate electrodes has tapered edges with a taper angle in a range of 3°
to 60°
. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An electronic equipment having a display device comprising:
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a substrate;
a first thin film transistor formed over the substrate, said first thin film transistor comprising;
a first semiconductor island including at least a first channel formation region, a second channel formation region, lightly doped regions and source and drain regions;
a first gate insulating film formed over the first semiconductor island;
a first gate electrode formed over the first channel formation region with the first gate insulating film interposed therebetween; and
a second gate electrode formed over the second channel formation region with the first gate insulating film interposed therebetween;
a driving circuit including at least one second thin film transistor formed over the substrate, said second thin film transistor comprising;
a second semiconductor island including at least a third channel formation region;
a second gate insulating film formed over the second semiconductor island;
a third gate electrode formed over the third channel formation region with the second gate insulating film interposed therebetween;
an interlayer insulating film covering the first, second and third gate electrodes and said first and second semiconductor islands; and
a pixel electrode formed over the interlayer insulating film and electrically connected to one of the source and drain regions of the first semiconductor island, wherein each of the first, second and third gate electrodes has tapered edges with a taper angle in a range of 3°
to 60°
,wherein each of said lightly doped regions is partly overlapped by tapered portions of the first or second gate electrode and extends beyond a side edge of the first or second gate electrode. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. An electronic equipment having a display device comprising:
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a substrate;
a first thin film transistor formed over the substrate, said first thin film transistor comprising;
a first semiconductor island including at least a first channel formation region, a second channel formation region, lightly doped regions, and a capacitor forming region;
a first gate insulating film formed over the first semiconductor island;
a first gate electrode formed over the first channel formation region with the first gate insulating film interposed therebetween;
a second gate electrode formed over the second channel formation region with the first gate insulating film interposed therebetween;
a driving circuit including at least one second thin film transistor formed over the substrate, said second thin film transistor comprising;
a second semiconductor island including at least a third channel formation region; and
a third gate electrode formed over the third channel formation region with the second gate insulating film interposed therebetween;
a capacitor electrode formed over the capacitor forming region of the first semiconductor island with an insulator interposed therebetween;
an interlayer insulating film covering the first, second and third gate electrodes and said first and second semiconductor islands;
a pixel electrode formed over the interlayer insulating film and electrically connected to an impurity region of the first semiconductor island, wherein each of the first, second and third gate electrodes and said capacitor electrode has tapered edges with a taper angle of in a range of 3°
to 60°
. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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22. An electronic equipment having a display device comprising:
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a substrate;
a first thin film transistor formed over the substrate, said first thin film transistor comprising;
a first semiconductor island including at least a first channel formation region, a second channel formation region, lightly doped regions and source and drain regions;
a first gate insulating film formed over the first semiconductor island;
a first gate electrode formed over the first channel formation region with the first gate insulating film interposed therebetween; and
a second gate electrode formed over the second channel formation region with the first gate insulating film interposed therebetween;
a driving circuit including at least one second thin film transistor formed over the substrate, said second thin film transistor comprising;
a second semiconductor island including at least a third channel formation region;
a second gate insulating film formed over the second semiconductor island;
a third gate electrode formed over the third channel formation region with the second gate insulating film interposed therebetween;
an interlayer insulating film covering the first, second and third gate electrodes and said first and second semiconductor islands; and
a pixel electrode formed over the interlayer insulating film and electrically connected to one of the source and drain regions of the first semiconductor island, wherein each of the first, second and third gate electrodes includes a lower conductive layer and an upper conductive layer formed on the lower conductive layer wherein said lower conductive layer extends beyond side edges of the upper conductive layer and extending portions of the lower conductive layer are tapered with a taper angle of 3°
to 60°
. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29)
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30. An electronic equipment having a display device comprising:
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a substrate;
a first thin film transistor formed over the substrate, said first thin film transistor comprising;
a first semiconductor island including at least a first channel formation region, a second channel formation region, lightly doped regions and source and drain regions;
a first gate insulating film formed over the first semiconductor island;
a first gate electrode formed over the first channel formation region with the first gate insulating film interposed therebetween; and
a second gate electrode formed over the second channel formation region with the first gate insulating film interposed therebetween;
a driving circuit including at least one second thin film transistor formed over the substrate, said second thin film transistor comprising;
a second semiconductor island including at least a third channel formation region;
a second gate insulating-film formed over the second semiconductor island;
a third gate electrode formed over the third channel formation region with the second gate insulating film interposed therebetween;
an interlayer insulating film covering the first, second and third gate electrodes and said first and second semiconductor islands; and
a pixel electrode formed over the interlayer insulating film and electrically connected to one of the source and drain regions of the first semiconductor island, wherein each of the first, second and third gate electrodes includes a lower conductive layer and an upper conductive layer formed on the lower conductive layer wherein said lower conductive layer extends beyond side edges of the upper conductive layer and extending portions of the lower conductive layer are tapered with a taper angle of 3°
to 60°
,wherein each of said lightly doped regions is partly overlapped by the extending portion of the first conductive layer of the first or second gate electrode and extends beyond a side edge of the first conductive layer of the first or second gate electrode. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37)
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38. An electronic equipment having a display device comprising:
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a substrate;
a first thin film transistor formed over the substrate, said first thin film transistor comprising;
a first semiconductor island including at least a first channel formation region, a second channel formation region, lightly doped regions, and a capacitor forming region;
a first gate insulating film formed over the first semiconductor island;
a first gate electrode formed over the first channel formation region with the first gate insulating film interposed therebetween;
a second gate electrode formed over the second channel formation region with the first gate insulating film interposed therebetween;
a driving circuit including at least one second thin film transistor formed over the substrate, said second thin film transistor comprising;
a second semiconductor island including at least a third channel formation region; and
a third gate electrode formed over the third channel formation region with the second gate insulating film interposed therebetween;
a capacitor electrode formed over the capacitor forming region of the first semiconductor island with an insulator interposed therebetween;
an interlayer insulating film covering the first, second and third gate electrodes and said first and second semiconductor islands;
a pixel electrode formed over the interlayer insulating film and electrically connected to an impurity region of the first semiconductor island, wherein each of the first, second and third gate electrodes includes a lower conductive layer and an upper conductive layer formed on the lower conductive layer wherein said lower conductive layer extends beyond side edges of the upper conductive layer and extending portions of the lower conductive layer are tapered with a taper angle of 3°
to 60°
. - View Dependent Claims (39, 40, 41, 42, 43, 44, 45)
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Specification