The present application provides a memory device having a memory cell with reduced protrusion protruding from the memory cell. The memory device includes a semiconductor substrate having a fin portion protruding from a surface of the semiconductor substrate; a semiconductive layer disposed conformal to the fin portion; a conductive layer disposed over the semiconductive layer; an insulating layer disposed over the conductive layer; and a protrusion including a first protruding portion laterally protruding from the semiconductive layer and along the surface, a second protruding portion laterally protruding from the conductive layer and over the first protruding portion, and a third protruding portion laterally protruding from the insulating layer and over the second protruding portion, wherein the protrusion has an undercut profile.