Display device with an improved contact hole arrangement for contacting a semiconductor layer through an insulation film

A display device being characterized in that the display device comprises:

• a thin film transistor formed in a polysilicon layer which includes a gate electrode, a channel region and drain and source regions arranged at both sides of the channel region which are formed over an insulation substrate;
• a metal film formed over the polysilicon layer;
• and
• an insulation film formed over the metal film and having a contact hole, formed over the metal film;
• wherein
• the contact hole is formed by anisotropic etching.

A display device being characterized in that the display device comprises:

• a semiconductor layer made of polysilicon which is comprised of a channel region and drain and source regions which are formed over an insulating substrate;
• a first insulating film formed over the drain and source regions;
• a contact hole formed in the first insulating film said contact hole is at least partially formed by anisotropic etching to minimize the size of the opening of the contact hole in an upper surface of the first insulating film;
• and
• means for preventing etching of the semiconductor film at the lower portion of the contact hole by the anisotropic etching.

A display device being characterized in that the display device comprises:

• a semiconductor layer made of polysilicon which includes a channel region and drain and source regions which are formed over an insulation substrate;
• a first insulating film formed over the drain and source regions;
• a conductive film formed over the first insulating film;
• and
• means for changing an angle of a side wall of the contact hole to have a greater angle at a location spaced apart from a main surface of the semiconductor layer in a vertical direction than at a location closer to the main surface of the semiconductor layer in said vertical direction to minimize the size of the opening of the contact hole in an upper surface of the first insulating film and for preventing disconnection between the semiconductor film and the conductive film.

A display device being characterized in that the display device comprises:

• a semiconductor layer made of polysilicon which includes a channel region and drain and source regions which are formed in a main surface of the semiconductor layer over an insulation substrate;
• and
• a first insulating film formed over said main surface and the drain and source regions;
• a gate electrode formed over the first insulating film;
• a second insulating film formed over the first insulating film and the gate electrode;
• and
• a contact hole extending in a vertical direction from said main surface through the first insulating film and the second insulating film, said contact hole including a first side surface and a second side surface arranged in said vertical direction so that said first side surface is farther from said main surface of the semiconductor layer in said vertical direction than said second side surface,
• where an angle of the first side surface with respect to the substrate is greater than an angle of the second side surface with respect to the substrate.