disclosed are a wafer carrier assembly and a chemical mechanical polishing apparatus including the same . the present wafer carrier for a chemical mechanical polishing apparatus comprises : a wafer carrier head rotatably mounted on the apparatus , having a lower surface for contacting a wafer ; a retaining ring attached to the lower surface of the wafer carrier head , for retaining or preventing the wafer from moving from the wafer carrier head during rotational motion thereof ; and a guard ring attached to the lower surface of the wafer carrier head a distance outside the retaining ring .