TFT with reduced parasitic capacitance
First Claim
Patent Images
1. A pixel for use in a liquid crystal display, comprising:
- a layer of liquid crystal material sandwiched between two spaced substrates, one of said substrates having a pixel electrode mounted thereon which defines a pixel surrounded by, ate and drain lines, wherein said pixel electrode is electrically connected to a thin film transistor, said thin film transistor comprising;
a drain electrode adapted to be electrically connected to said drain line;
a gate electrode adapted to be electrically connected to said gate line; and
a source electrode electrically connected to said pixel electrode;
wherein said source electrode is located on a semiconductor film and is substantially completely surrounded in substantially all lateral directions by said drain electrode, and wherein said drain electrode is disposed between said source electrode and at least a substantial portion of said pixel electrode so that said transistor has a reduced parasitic capacitance.
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Abstract
A thin film transistor (TFT) array in an active matrix liquid crystal display (AMLCD) including a centrally located round source electrode substantially completely surrounded by a substantially annular or circular shaped drain electrode. The geometric design of the TFT of this invention provides for a thin film transistor having a reduced parasitic capacitance and decreased photosensitivity. The TFTs of this invention are located at the intersections of gate and drain lines of an active matrix LCD array thereby increasing the size of the pixel display openings of the matrix array.
191 Citations
22 Claims
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1. A pixel for use in a liquid crystal display, comprising:
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a layer of liquid crystal material sandwiched between two spaced substrates, one of said substrates having a pixel electrode mounted thereon which defines a pixel surrounded by, ate and drain lines, wherein said pixel electrode is electrically connected to a thin film transistor, said thin film transistor comprising; a drain electrode adapted to be electrically connected to said drain line;
a gate electrode adapted to be electrically connected to said gate line; and
a source electrode electrically connected to said pixel electrode;
wherein said source electrode is located on a semiconductor film and is substantially completely surrounded in substantially all lateral directions by said drain electrode, and wherein said drain electrode is disposed between said source electrode and at least a substantial portion of said pixel electrode so that said transistor has a reduced parasitic capacitance. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 20, 21)
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9. In an active matrix liquid crystal display (AMLCD) comprising a plurality of thin film transistors arranged on an insulating substrate in the form of a matrix, at least one of said plurality of thin film transistors including a drain electrode electrically connected to a drain line, a gate electrode electrically connected to a gate line, and a source electrode electrically connected to a transparent pixel electrode of a corresponding picture element or pixel, wherein said source and drain electrodes of said at least one thin film transistor are formed on a semiconductor film and separated from one another by a channel defining a predetermined length and width, the improvement comprising:
wherein said source electrode of said at least one thin film transistor is centrally located on said semiconductor film and is substantially completely surrounded laterally by said drain electrode, and wherein said drain electrode is positioned between said source electrode and said picture element. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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22. A liquid crystal display comprising:
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a plurality of TFTs which act as switching elements for corresponding pixels, said TFTs being laterally spaced from the picture defining portions of said pixels; and wherein each of said TFTs includes a gate electrode and a centrally located source electrode substantially surrounded by a drain electrode whereby said TFTs have reduced parasitic capacitances.
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Specification