Light emitting device

• US 6,690,034 B2
• Filed: 07/27/2001
• Issued: 02/10/2004
• Est. Priority Date: 07/31/2000
• Status: Expired due to Term

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Murakami, Satoshi, Fujimoto, Etsuko, Inukai, Kazutaka
• Primary Examiner(s): Whitehead, Jr., Carl
• Assistant Examiner(s): Vesperman, William C.
• Application Number:
  US09/915,539
• Publication Number:
  US 20020011597A1
• Time in Patent Office: 928 Days
• Field of Search: 257/72, 257/79, 257/98
• US Class Current: 257/72
• CPC Class Codes: H01L 2029/7863 with an LDD consisting of more than one lightly doped zone or having a non-homogeneous dopant distribution, e.g. graded LDD
• CPC Class Codes: H01L 27/1214 comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
• CPC Class Codes: H01L 27/124 with a particular composition, shape or layout of the wiring layers specially adapted to the circuit arrangement, e.g. scanning lines in LCD pixel circuits wiring structures per se H01L23/52
• CPC Class Codes: H01L 27/1259 Multistep manufacturing methods
• CPC Class Codes: H01L 27/127 with a particular formation, treatment or patterning of the active layer specially adapted to the circuit arrangement
• CPC Class Codes: H01L 29/66757 Lateral single gate single channel transistors with non-inverted structure, i.e. the channel layer is formed before the gate
• CPC Class Codes: H01L 29/78621 with LDD structure or an extension or an offset region or characterised by the doping profile
• CPC Class Codes: H10K 59/1213 the pixel elements being TFTs

Abstract

There is provided a light emitting device including a TFT having a high driving capacity (on current) and high reliability in a driver circuit and a TFT in which an off current is reduced in a pixel portion. In manufacturing the TFTs, after the TFT having an LDD region is formed, a part of a gate electrode is etched to form the TFT having GOLD region. Thus, the TFTs having required functions can be easily formed in the driver circuit and the pixel portion, respectively, on the same substrate.

Claims

1. A light emitting device comprising:

a switching TFT provided over a substrate;

an erase TFT provided over the substrate;

a current control TFT provided over the substrate; and

an EL element provided over the substrate,

wherein the switching TFT and the erase TFT and the current control TFT and the EL element are provided in a pixel,

wherein drain regions of the switching TFT and the erase TFT are electrically connected with a gate electrode of the current control TFT,

wherein a drain region of the current control TFT is electrically connected with the EL element, and

wherein gate electrodes of the switching TFT and the erase TFT exist at respective positions where the gate electrodes do not overlap impurity regions of the switching TFT and the erase TFT, respectively, through a gate insulating film.

2. A device according to claim 1, wherein the gate electrode of the switching TFT exists at a position where the gate electrode overlaps a low concentration impurity region of the switching TFT through the gate insulating film.

3. A device according to claim 1, wherein the current control TFT is a p-channel type.

4. A device according to claim 1, wherein the switching TFT is an n-channel type.

5. A device according to claim 1, wherein a driver circuit formed on the substrate is constituted of an n-channel TFT and a p-channel TFT, and a gate electrode of the n-channel TFT exists at a position where the gate electrode overlaps a low concentration impurity region of the n-channel TFT.

6. Electric equipment using the light emitting device according to claim 1.

7. A device according to claim 1, wherein the light emitting device is one selected from the group consisting of a display device, a video camera, a head mounted display, a portable image playback device equipped with a recording medium, a goggle type display device, a personal computer, a portable telephone, a sound playback device, and a digital camera.

8. A device according to claim 1, wherein a plurality of the current control TFTs are included in a pixel.