Cross point type dram cell composed of a pillar having an active region

Abstract

A dynamic random access memory (DRAM) device comprises a substrate, a plurality of substantially parallel word lines, and a plurality of substantially parallel bit lines. A plurality of memory cells are formed at intersections of the word lines and bit lines. Each of the memory cells includes a pillar of semiconductor material which extends outward from the substrate. A storage node plug extends from a storage node through the pillar to a storage node contact and one of a drain and a source of a MOS transistor. A bit line plug extends from the bit line inwardly to the outer surface of the pillar to form a bit line contact and the other of the drain and the source of the MOS transistor. A word line plug extends from the word line through the pillar and a portion of the word line plug forms a gate of the MOS transistor. The storage node plug, bit line plug, and word line plug can be formed asymmetrically as substantially solid, unitary structures having a desired thickness for ease in manufacturing. A method for manufacturing such a device is also disclosed, and requires only four masks.