Patent ID: 7463510
Filing Date: 2008-12-09
Classification: G11C

Abstract:
1. A magnetoresistive random access memory (MRAM) device formed on a substrate, comprising: a read bit line; two or more write bit lines; a read word line; a write word line substantially perpendicular to the write bit lines; and a memory cell corresponding to the read bit line, the read word line, the write word line, and the two or more the write bit lines, wherein the memory cell comprises a first memory unit and a second memory unit, each respective memory unit corresponding to a respective write bit line, and each memory unit comprising: wherein the first memory unit has one of two resistances: a first resistance when a magnetic moment of the free magnetic region of the first memory unit is parallel to a magnetic moment of the pinned magnetic region; and a second resistance when the magnetic moment of the free magnetic region of the first memory unit is anti-parallel to the magnetic moment of the pinned magnetic region, wherein the second memory unit has one of two resistances: a third resistance when the magnetic moment of the free magnetic region of the second memory unit is parallel to the magnetic moment of the pinned magnetic region; and a fourth resistance when the magnetic moment of the free magnetic region of the second memory unit is anti-parallel to the magnetic moment of the pinned magnetic region, wherein the first resistance, the second resistance, the third resistance, and the fourth resistance are different values of resistance, and wherein the first memory unit has a first cross-sectional area and the second memory unit has a second cross-sectional area smaller than the first cross-sectional area, the first and second cross-sectional areas respectively corresponding to a plane substantially perpendicular to first and second read current flows; and wherein the first cross-sectional area is about 2 times the second cross-sectional area.