1. Field of Invention
The present disclosure of invention relates to a liquid crystal display (LCD) and a method of fabricating the same, and more particularly, to a liquid crystal display (LCD), which includes thin film transistors (TFTs) that can be mass produced more efficiently (fewer process steps) and more reliability (due to fewer masking steps and due to self-alignment plus monolithic integration of parts).
2. Description of Related Technology
A liquid crystal display (LCD) typically includes a first substrate having a plurality of pixel electrodes provided thereon, a second substrate having a one or more common electrodes provided thereon, and a liquid crystal molecular layer which has dielectric anisotropy and is interposed between the first and second substrates. The LCD can selectively change the alignment of liquid crystal molecules in the liquid crystal molecular layer by forming different electric field orientations between specific ones of the pixel electrodes and the one or more common electrodes and/or by adjusting the intensity of the formed electric fields. In so doing, the LCD can control the amount of light transmitting through the liquid crystal molecular layer and can thus display a desired image. Thin film transistors (TFTs) are widely used as switching devices for controlling the electric fields formed in such LCDs.
A TFT is a switching device which can be integrally formed on a transparent substrate and typically includes a semiconductive active layer (e.g., amorphous silicon) having a gate electrode formed over a channel portion of the active layer, a source electrode at one side, and a drain electrode spaced away at another side of the channel portion. (Incidentally, the definition of which is the source electrode and which is the drain electrode of a TFT can vary and is sometimes swapped. Suffice it to say here that the TFT includes spaced apart source/drain regions with a channel region therebetween where conduction of charge carriers through the channel region can be selectively switched on and off.) When a voltage higher than a predetermined threshold level (Vt) is applied to the gate electrode, a channel regions in the active layer becomes conductive. This allows an electric current to flow between the source electrode and the drain electrode. The active layer of the TFT may be made of amorphous silicon (a-Si) or polysilicon (p-Si). In addition, the TFT may have a top-gate structure, in which the gate electrode is disposed above the active layer, or a bottom-gate structure, in which the gate electrode is disposed under the active layer.
Typically, a connection via is formed between a given one of the source/drain regions of a TFT and a separate pixel-electrode so that the two are in good electrical communication with one another. However, during mass production, providing precise alignment of the via between given source/drain region and the pixel-electrode and providing consistently good electrical communication through the via can be problematic.