In recent years, attention has focused on a technique for making a thin film transistor (TFT) by using a semiconductor thin film (having a thickness of approximately several to several hundreds of nanometers) formed over a substrate having an insulating surface. The thin film transistors are widely applied to electronic devices such as ICs and electro-optical devices, and in particular their rapid development as switching elements for image display devices is desired.
A liquid crystal display device is known as an example of an image display device. Compared to passive matrix liquid crystal display devices, high-definition images can be obtained with active matrix liquid crystal display devices; therefore, active matrix liquid crystal display devices have become widely used. In an active matrix liquid crystal display device, when pixel electrodes arranged in matrix are driven, a display pattern is displayed on a screen. In more detail, when voltage is applied between a selected pixel electrode and a counter electrode that corresponds to the selected pixel electrode, a liquid crystal layer provided between the pixel electrode and the counter electrode is optically modulated, and this optical modulation is recognized as a display pattern by an observer.
In a common transmissive-type liquid crystal display device, a liquid crystal layer is provided between a pair of substrates, a first polarizing plate is provided on an outer surface side of one of the pair of substrates which is a first substrate (a substrate provided with a pixel electrode), which is not a side in contact with the liquid crystal layer, and a second polarizing plate is provided on an outer surface side of the other one of the pair of substrates which is a second substrate (a counter substrate), which is not the side in contact with the liquid crystal layer.
When a color filter is used for displaying full color, the color filter is generally provided on a surface which is not the surface of the substrate where the polarizing plate is provided (the counter substrate). In other words, the color filter is generally provided between the counter substrate and the liquid crystal layer.
A spacer for maintaining the gap between the substrates is provided between the pair of substrates, and a particulate bead spacer or a columnar spacer is provided. In the case where a columnar spacer formed of a transparent resin is provided on the counter substrate, there has been a concern about a TFT overlapping with the columnar spacer breaking due to pressure from when the substrate is attached to the other substrate. Accordingly, the degree of precision of attachment of the pair of substrates affects the yield.
The applicant has disclosed a technique of forming a columnar spacer over a substrate on which a TFT serving as a switching element of a pixel portion is formed, in Patent Document 1 (Japanese Published Patent Application No. 2001-75500). In addition, the applicant has disclosed a technique of forming a black matrix formed of an organic resin over a TFT in Patent Document 2 (Japanese Published Patent Application No. H9-105953).