A phase change memory device capable of increasing a sensing margin and a method for manufacturing the same. The phase change memory device includes a semiconductor substrate formed with a device isolation structure which defines active regions; first conductivity type impurity regions formed in surfaces of the active regions and having the shape of a line; a second conductivity type well formed in the semiconductor substrate at a position lower than the device isolation structure; a second conductivity type ion-implantation layer formed in the semiconductor substrate at a boundary between a lower end of the device isolation structure and the semiconductor substrate; a plurality of vertical PN diodes formed on the first conductivity type impurity regions; and phase change memory cells formed on the vertical PN diodes.