Liquid crystal display device and fabrication method of the same

Abstract

The invention relates to an active matrix liquid crystal display device which uses a switching device to control a pixel, and an object is to provide a liquid crystal display device which has an excellent viewing angle property and high brightness and a fabrication method of the same. A TFT substrate has a structure which reduces the film thickness of a protective insulating film in a control capacitance part in which control capacitance is formed and the film thickness of a protective insulating film in an auxiliary capacitance part in which auxiliary capacitance is formed thinner than the film thickness of a protective insulating film which covers a TFT and the other elements.

1 . A liquid crystal display device comprising:
 first and second substrates which are disposed as they face each other;   vertical alignment type liquid crystals which are sealed between the first and the second substrates;   a plurality of gate bus lines which are disposed on the first substrate and to which a scanning signal is supplied;   a plurality of data bus lines which are disposed on the first substrate as they intersects with the gate bus lines and to which a display signal is supplied;   a switching device which is formed in every pixel area, the area being defined by the gate bus lines and the data bus lines;   a pixel electrode which is formed at each of the pixel areas;   a control electrode which is disposed in the pixel area and connected to the switching device; and   a protective insulating film which is disposed below the pixel electrodes and which covers the gate bus lines, the data bus lines, the switching devices and the control electrodes,   wherein the pixel electrode is split into at least first and second areas,   the pixel electrode in the first area is electrically connected to the control electrode, and   the pixel electrode in the second area is capacitively coupled through the control electrode and the protective insulating film,   wherein at least one part of the protective insulating film sandwiched between the pixel electrode in the second area and the control electrode is formed to have a film thickness thinner than that of the protective insulating film which covers other portions.   
     
     
         2 . The liquid crystal display device according to  claim 1 , wherein the protective insulating film which covers the gate bus lines, the data bus lines, and the switching devices is formed of at least first and second layers from below, and
 at least one part of the protective insulating film sandwiched between the pixel electrode in the second area and the control electrode is formed of only the first layer.   
     
     
         3 - 4 . (canceled) 
     
     
         5 . A liquid crystal display device comprising:
 first and second substrates which are disposed as they face each other;   liquid crystals which are sealed between the first and the second substrates;   a plurality of gate bus lines which are disposed on the first substrate and to which a scanning signal is supplied;   a plurality of auxiliary capacitance electrodes which are formed at the same time to form the gate bus lines;   an insulating film which is formed above the gate bus lines and the auxiliary capacitance electrodes and one part of which functions as a gate insulating film;   a plurality of data bus lines which are disposed on the first substrate as they intersects with the gate bus lines and to which a display signal is supplied;   a switching device which is formed in every pixel area, the area being defined by the gate bus lines and the data bus lines;   a pixel electrode which is electrically connected to the switching device;   a protective insulating film which is disposed below the pixel electrodes and which covers the gate bus lines, the data bus lines and the switching devices; and   an auxiliary capacitance which is formed between the pixel electrode and the auxiliary capacitance electrode,   wherein the protective insulating film which covers the switching device is formed of at least first and second layers from below and the second layer is removed in the protective insulating film above the auxiliary capacitance electrode, and   the auxiliary capacitance is formed of the insulating film and the first layer of the protective insulating film.   
     
     
         6 . A fabrication method of a liquid crystal display device comprising the steps of:
 forming a gate bus line, a data bus line, a switching device and a control electrode on a first substrate and then forming a protective insulating film over throughout a front surface of the first substrate;   coating a photoresist over throughout the front surface of the protective insulating film, exposing and developing the photoresist so that the photoresist is removed in a portion which electrically connects the control electrode to a pixel electrode in a first area, and a film thickness of the photoresist on the protective insulating film sandwiched between the control electrode and a pixel electrode in a second area is thinner than that of the photoresist to remain in other portions;   etching the protective insulating film in the portion which electrically connects the control electrode to the pixel electrode in the first area and uncovering the control electrode;   removing the photoresist formed thin on the protective insulating film sandwiched between the control electrode and the pixel electrode in the second area and leaving the photoresist on the protective insulating film in other portions;   etching one part of a film thickness of the protective insulating film sandwiched between the control electrode and the pixel electrode in the second area and reducing the film thickness of the protective insulating film;   removing all of the photoresist; and   forming the pixel electrodes in the first and the second areas on the protective insulating film.   
     
     
         7 . A fabrication method of a liquid crystal display device comprising the steps of:
 forming a gate bus line, an auxiliary capacitance electrode, an insulating film one part of which functions as a gate insulating film, a data bus line, and a switching device on a first substrate and then forming a protective insulating film over throughout a front surface of the first substrate;   coating a photoresist over throughout the front surface of the protective insulating film, exposing and developing the photoresist so that the photoresist is removed in a terminal lead part of the gate bus line, and a film thickness of the photoresist on the protective insulating film in a portion which electrically connects the switching device to a pixel electrode and in a portion in which an auxiliary capacitance is formed is thinner than that of the photoresist to remain in other portions;   etching the protective insulating film in a terminal lead part of the gate bus line and the insulating film;   removing the photoresist formed thin on the protective insulating film in the portion which electrically connects the switching device to the pixel electrode and in the portion in which the auxiliary capacitance is formed and leaving the photoresist on the protective insulating film in other portions;   etching all of the protective insulating film in the portion which electrically connects the switching device to the pixel electrode and the portion in which the auxiliary capacitance is formed;   removing all the photoresist; and   forming the pixel electrode on the protective insulating film and the insulating film.