Thin Film Transistor Structure

Abstract

A thin film transistor (TFT) structure is provided. The TFT comprises a gate, a first electrode, a second electrode, a dielectric layer, and a channel layer. By overlapping the area between the first electrode and the gate, the TFT structure acquires a parasitic capacitor that is unaffected by manufacture deviations. Therefore, the TFT needs no compensation capacitor, thereby, increasing the aperture ratio of the TFT.

1 . A thin film transistor (TFT) structure for a liquid crystal display (LCD) having a scan line a data line, a first pixel electrode and a second pixel electrode, the thin film transistor comprising:
 a gate electrode, connecting to the scan line;   a dielectric layer, covering the gate electrode;   a first patterned channel layer, disposed on the dielectric layer and above the gate electrode;   a second patterned channel layer, disposed on the dielectric layer and above the gate electrode adjacent to the first patterned channel layer;   a first electrode, connected to the data line, the first electrode having a first portion disposed on a portion of the first patterned channel layer and a second portion disposed on a portion of the second patterned layer;   a second electrode, disposed on another portion of the first patterned channel layer and electrically connected to the first pixel electrode, the second electrode including at least two branches substantially parallel to the first portion of the first electrode and extending along a first direction, the branches of the second electrode and the first portion of the first electrode being alternately disposed on the first patterned channel layer with at least two first channels therebetween;   a third electrode, disposed on another portion of the second patterned channel layer and electrically connected to the second pixel electrode, the third electrode being extending along a second direction substantially perpendicular to the first direction, the third electrode and the second portion of the first electrode being disposed on the second patterned channel layer with a second channel therebetween;   wherein a channel width-to-length (W-L) ratio of each of the first channels is larger than a channel width-to-length (W-L) ratio of the second channel.   
     
     
         2 . The thin film transistor structure of  claim 1 , wherein the gate electrode, the dielectric layer, the first patterned channel layer, the first electrode and the second electrode construct a primary thin film transistor (TFT) structure. 
     
     
         3 . The thin film transistor structure of  claim 2 , wherein one of the first electrode and the second electrode is a source electrode of the primary thin film transistor structure, and the other one of the first electrode and the second electrode is a drain electrode of the primary thin film transistor structure. 
     
     
         4 . The thin film transistor structure of  claim 1 , wherein the gate electrode, the dielectric layer, the first patterned channel layer, the first electrode and the third electrode construct an auxiliary thin film transistor (TFT) structure. 
     
     
         5 . The thin film transistor structure of  claim 4 , wherein one of the first electrode and the third electrode is a source electrode of the auxiliary thin film transistor structure, and the other one of the first electrode and the third electrode is a drain electrode of the auxiliary thin film transistor structure. 
     
     
         6 . The thin film transistor structure of  claim 1 , wherein the dielectric layer is made of a material comprising silicon nitride. 
     
     
         7 . The thin film transistor structure of  claim 1 , wherein the first patterned channel layer is made of a material comprising amorphous silicon. 
     
     
         8 . The thin film transistor structure of  claim 1 , wherein the second patterned channel layer is made of a material comprising amorphous silicon. 
     
     
         9 . The thin film transistor structure of  claim 1 , wherein each of the first electrode, the second electrode and the third electrode has a width about 1-10 micrometers. 
     
     
         10 . A pixel structure for a liquid crystal display (LCD), comprising:
 a scan line a data line, a first pixel electrode and a second pixel electrode; and   a thin film transistor, comprising:   a gate electrode, connecting to the scan line;   a dielectric layer, covering the gate electrode;   a first patterned channel layer, disposed on the dielectric layer and above the gate electrode;   a second patterned channel layer, disposed on the dielectric layer and above the gate electrode adjacent to the first patterned channel layer;   a first electrode, connected to the data line, the first electrode having a first portion disposed on a portion of the first patterned channel layer and a second portion disposed on a portion of the second patterned layer;   a second electrode, disposed on another portion of the first patterned channel layer and electrically connected to the first pixel electrode, the second electrode including at least two branches substantially parallel to the first portion of the first electrode and extending along a first direction, the branches of the second electrode and the first portion of the first electrode being alternately disposed on the first patterned channel layer with at least two first channels therebetween;   a third electrode, disposed on another portion of the second patterned channel layer and electrically connected to the second pixel electrode, the third electrode being extending along a second direction substantially perpendicular to the first direction, the third electrode and the second portion of the first electrode being disposed on the second patterned channel layer with a second channel therebetween;   wherein a channel width-to-length (W-L) ratio of each of the first channels is larger than a channel width-to-length (W-L) ratio of the second channel.