Active solid-state devices (e.g. – transistors – solid-state diode – Non-single crystal – or recrystallized – semiconductor... – Amorphous semiconductor material
Reexamination Certificate
1999-07-30
2001-12-11
Meier, Stephen D. (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Non-single crystal, or recrystallized, semiconductor...
Amorphous semiconductor material
C257S057000
Reexamination Certificate
active
06329673
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to display apparatuses, and more particularly, to a driving circuit formed of circuit devices having large variations in characteristics such as thin-film transistors (TFTs), used for a display apparatus, such as a liquid-crystal display apparatus.
2. Description of the Related Art
In display apparatuses, such as liquid-crystal display apparatuses, especially in so-called “driving-circuit-integrated liquid-crystal display apparatuses,” in each of which a driving circuit for driving pixels is integratedly built in an active-matrix liquid-crystal panel in which the pixels formed of thin-film transistors serving as active devices are disposed in a matrix, the driving circuit itself is also constructed of thin-film transistors.
In general, thin-film transistors have variations in characteristics, such as on-current characteristics, because they have uneven crystalline grain coarsenesses, i.e., uneven-sized crystalline grains.
When a driving circuit for a display apparatus, especially a switching section and an input-voltage conversion circuit for an analog-operation video line, is formed of circuit devices having large variations in characteristics, such as thin-film transistors, these device-characteristic variations adversely affect circuit operations. The video-signal switching section may cause a vertical line to appear, deteriorating uniformity. In the input-voltage conversion circuit, circuit malfunction may occur.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a display apparatus having an improved yield and improved image quality by suppressing variations in transistor characteristics.
Another object of the present invention is to provide transistors having suppressed characteristic variations.
One of the foregoing objects is achieved in one aspect of the present invention through the provision of a liquid-crystal display apparatus including a first substrate in which a pixel section having pixel electrodes and a driving section for driving the pixel section are formed; a second substrate disposed such that it opposes the first substrate with a predetermined gap therebetween; and a liquid-crystal layer held between the first substrate and the second substrate; wherein a circuit device constituting the driving circuit for driving the pixel section is made from a transistor having a gate length of nL and a gate width of nW (n is any number exceeding one), where L indicates the shortest gate length determined from the dielectric strength and W indicates the gate width determined from a given ratio of W/L according to the shortest gate length L.
One of the foregoing objects is achieved in another aspect of the present invention through the provision of a transistor including a substrate; a channel region on the substrate; a gate insulating film on the substrate; a source region having a source electrode on the substrate; a drain region having a drain electrode on the substrate; and a gate electrode on the substrate having a gate length of nL and a gate width of nW (n is any number exceeding one), where L indicates the shortest gate length determined from the dielectric strength and W indicates the gate width determined from a given ratio of W/L according to the shortest gate length L.
One of the foregoing objects is achieved in still another aspect of the present invention through the provision of a display apparatus including a substrate; a pixel section on the substrate; and a driving section for driving the pixel section on the substrate; wherein a circuit device constituting the driving circuit for driving the pixel section is made from a transistor having a gate length of nL and a gate width of nW (n is any number exceeding one), where L indicates the shortest gate length determined from the dielectric strength and W indicates the gate width determined from a given ratio of W/L according to the shortest gate length L.
In the above display apparatus, the gate length of a transistor is determined from its dielectric strength. To reduce the size of a circuit, it is necessary, in general, to reduce the size of the transistors used. The shortest gate length L determined from the dielectric strength is set first. A gate width W is set from the ratio W/L (gate width/gate length) by the use of the shortest gate length L according to the purpose of use.
When a transistor size is specified with the ratio W/L being maintained and the gate length and the gate width being set to n times those described above, since the area below the gate electrode is extended, variations in the sizes of the silicon crystalline grains in the channel regions can be ignored. With these settings, variations in transistor characteristics are suppressed without changing transistor on-currents.
REFERENCES:
patent: 6023075 (2000-02-01), Yamazaki
Muller et al, Device Electronics for Integrated Circuits, p. 439, 1986.
Hayashi Yuji
Iida Masayuki
Kananen Ronald P.
Meier Stephen D.
Rader & Fishman & Grauer, PLLC
Sony Corporation
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