The present application provides a method of manufacturing a memory device having a word line (WL) with improved adhesion between a work function member and a conductive layer. The method includes steps of providing a semiconductor substrate defined with an active area and including an isolation structure surrounding the active area; forming a recess extending into the semiconductor substrate and across the active area; forming a first insulating layer conformal to the recess; disposing a first conductive material conformal to the first insulating layer; forming a conductive member surrounded by the first conductive material; disposing a second conductive material over the conductive member and removing a portion of the first conductive material above the second conductive material to form a conductive layer enclosing the conductive member; and forming a second insulating layer over the conductive layer and conformal to the first insulating layer.