Abstract: An improved chemical mechanical polishing apparatus for polishing a semiconductor wafer used in the fabrication of silicon-based semiconductor devices is provided so as to eliminate an air pocket bubble from being formed underneath a polishing pad without the need for cutting the same. This is achieved by a CMP platen plug which is disposed in a recess formed in a top cover plate member so as to completely fill the recess in order to displace the air pocket. The polishing pad is then secured over the platen plug and the top cover plate member. As a result, the useful life of the polishing pad has been prolonged.