1. Field of the Invention
The present invention relates generally to semiconductor processing technology, and more particularly, to a semiconductor device and manufacturing method thereof.
2. Description of the Related Art
In semiconductor processes, after etching a contact hole over a metal gate, the metal gate exposed to air trends to form metal oxide. For example, aluminum (AL) exposed to air trends to form aluminum oxide. It is hard to remove the metal oxide formed on the metal gate.
FIG. 1A and FIG. 1B show a sequence of cross sectional views illustrating a conventional method of forming a metal gate in a semiconductor device. As shown in FIG. 1A, a semiconductor device has a contact hole 106 formed over a metal gate 102 and a contact hole 108 formed over an active area 104. As further shown in FIG. 1A, a surface of the metal gate 102 and a surface of the active area are exposed after forming the contact holes 106 and 108. The surface of the metal gate 102 exposed to air will form metal oxide which should be removed. Referring next to FIG. 1B, the metal oxide formed on the metal gate 102 is removed. Removing the metal oxide on the metal gate 102 can result in an undesired removal of a portion of a material (such as metal silicide region 104) at the bottom of the contact hole 108, thereby degrading the performance of the semiconductor device.