1. Field of Invention
The present invention relates to a semiconductor device having a circuit including a thin film transistor (hereinafter referred to as a TFT), and a method for manufacturing the same. For example, the invention relates to an electronic device which mounts a light emitting display device having a TFT and an organic light emitting element as its component.
In this specification, the term semiconductor device refers to a device in general that utilizes semiconductor characteristics to function, and a display device, an electro-optical device, a semiconductor circuit and an electronic device are all included in the semiconductor device.
2. Description of the Related Art
In recent years, the development for a liquid crystal display device and an Electro Luminescence display device in which a TFT is integrated on a glass substrate has been progressed. In each of these display devices, a thin film transistor is formed on a glass substrate using a thin film formation technique and a liquid crystal element or a light emitting element (electroluminescence element, hereinafter referred to as just an EL element) is formed on various circuits including the thin film transistor as a display element, thereby making it function as a display device.
The circuit including a TFT cause unevenness to some extent. Thus, when a liquid crystal element or an EL element is formed over the circuit, planarization using an organic resin film or the like is generally conducted (For example, Reference 1: Japanese Patent Laid-Open No. Hei 11-111693). Each pixel provided in a display portion of a semiconductor device has a pixel electrode therein. The pixel electrode is connected with the TFT through a contact hole provided in the above-mentioned organic resin film for planarization.
When an etching residue is left in the contact hole due to insufficient etching, there is a possibility that a wiring resistance is changed, or defective coverage is caused, thereby resulting in poor quality or characteristics when a wiring is formed.
A response to the above-mentioned insufficient etching is attempted (for example, Reference 1: Japanese Patent Laid-Open No. Hei 11-111693). In the Reference 1, a method for detecting a residue and removing the residue in the contact hole again after forming the contact hole, is disclosed.
However, a method described in the Reference 1, plural etching steps are required; therefore, productivity decreases due to increase in the steps. In addition, there is no effect of reducing a residue in the step itself since the etching step in itself is a conventional method.