1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly, to a Metal Oxide Semiconductor (referred to as ‘MOS’ hereinafter) transistor and a method for fabrication the same.
2. Description of the Related Art
In an MOS transistor, impurities are implanted and diffused in a semiconductor substrate such as silicon to make a source region and a drain region. A voltage is applied to the substrate and a gate isolated by an insulating layer such as an oxide layer to control a channel formation between the source and the drain. When a channel is formed by the gate voltage, an electric current flows between the source and the drain to cause the transistor become conductive. In contrast to this, when the channel is not formed, the transistor remains non-conductive, in which the electric current does not flow.
A MOS transistor according to the related art is either a 3 terminal device including a gate, a source, and a drain, or a 4 terminal device including the gate, the source, and the drain, and the substrate or a well electrode. An operation of the MOS transistor is controlled according to a bias voltage applied to the gate thereof. Accordingly, a method for controlling an electric current may be limited, and there is a limit to a current drive performance.
Moreover, so as to secure a voltage, the gate electrode should have a greater size than a predetermined value. Accordingly, it has a problem in that the size of the semiconductor device cannot be reduced.