Electronic device and electronic apparatus
AssigneeSemiconductor Energy Laborayory Co., Ltd.
InventorsYukio Yamauchi, Takeshi Fukunaga
Life of this patent
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Abstract
An EL display having high operating performance and reliability is provided. LDD regions 15a through 15d of a switching TFT 201 formed in a pixel are formed such that they do not overlap gate electrodes 19a and 19b to provide a structure which is primarily intended for the reduction of an off-current. An LDD region 22 of a current control TFT 202 is formed such that it partially overlaps a gate electrode 35 to provide a structure which is primarily intended for the prevention of hot carrier injection and the reduction of an off-current. Appropriate TFT structures are thus provided depending on required functions to improve operational performance and reliability.
Claims32
An electronic device having at least one pixel, said pixel comprising:
- a first TFT for switching, a second TFT for controlling current and an EL element connected to said second TFT;
- wherein an LDD (lightly-doped-drain) region formed in said first TFT does not overlap a gate electrode of said first TFT with a gate insulating film interposed,
- wherein an LDD region formed in said second TFT partially or entirely overlaps a gate electrode of said second TFT with a gate insulating film interposed.
An electronic device having at least one pixel, said pixel comprising:
- a first TFT for switching, a second TFT for controlling current and an EL element connected to said second TFT;
- wherein an LDD (lightly-doped-drain) region of said first TFT partially overlaps a gate electrode of said first TFT with a gate insulation film interposed,
- wherein an LDD region of said second TFT partially or entirely overlaps a gate electrode of said second TFT with a gate insulation film interposed.
An electronic device having a pixel portion and a driving circuit portion formed on an insulating surface,
- said driving circuit portion comprising:
- at least one n-channel type TFT having an LDD (lightly-doped-drain) region partially or entirely overlapping a gate electrode with a gate insulation film interposed, and
- said pixel portion comprising:
- a pixel including a first TFT for switching, a second TFT for controlling current and an EL element connected to said second TFT;
- wherein an LDD region of said first TFT does not overlap a gate electrode of said first TFT with a gate insulation film interposed;
- and
- wherein an LDD region of said second TFT partially or entirely overlaps a gate electrode of said second TFT with a gate insulation film interposed.
An electronic device having a pixel portion and a driving circuit portion formed on an insulating surface,
- said driving circuit portion comprising:
- at least one n-channel type TFT having an LDD (lightly-doped-drain) region partially or entirely overlapping a gate electrode with a gate insulation film interposed, and
- said pixel portion comprising:
- a pixel including a first TFT for switching, a second TFT for controlling current and an EL element connected to said second TFT;
- wherein an LDD region of said first TFT overlaps a gate electrode of said first TFT with a gate insulation film interposed;
- and
- wherein an LDD region of said second TFT partially or entirely overlaps a gate electrode of said second TFT with a gate insulation film interposed.
An electronic device having at least one pixel, said pixel comprising:
- a switching TFT;
- a current-control TFT connected to said switching TFT;
- an EL element connected to said current-control TFT,
- wherein an LDD (lightly-doped-drain) region formed in said switching TFT does not overlap a gate electrode of said switching TFT with a gate insulating film interposed,
- wherein an LDD region formed in said current-control TFT partially or entirely overlaps a gate electrode of said current-control TFT with a gate insulating film interposed,
- wherein an n-type impurity element is contained in the LDD region of said current-control TFT at a higher concentration higher than that of the LDD region of said switching TFT.
An electronic device having at least one pixel, said pixel comprising:
- a switching TFT;
- a current-control TFT connected to said switching TFT;
- an EL element connected to said current-control TFT;
- wherein an LDD (lightly-doped-drain) region formed in said switching TFT does not overlap a gate electrode of said switching TFT with a gate insulating film interposed,
- wherein an LDD region formed in said current-control TFT partially or entirely overlaps a gate electrode of said current-control TFT with a gate insulating film interposed,
- wherein a length of the LDD region overlapping the gate electrode of said current-control TFT is in the range from 1 to 3 μm.
Dependencies are inferred from the claim text.