A memory cell in a so-called MRAM by utilizing a tunnel magnetic resistance in the prior art has raised problems that a magnetic field to be applied to a TMR element is essentially weak since a word line for write is disposed apart from the TMR element, that a large current is required at the time of a writing operation, and that electric power consumption is large. In order to solve the above-described problems experienced in the prior art, the present invention provides an MRAM memory cell structure and its fabricating method in which a word line for write is disposed near a TMR element and surrounds it in three directions.
An MTJ MRAM cell is formed above or below an intersection of vertically separated, magnetically clad, ultra-thin orthogonal word and bit lines whose thickness is less than 100 nm. Lines of this thickness produce switching magnetic fields at the cell free layer that are enhanced by a factor of approximately two for a given current. The word and bit lines also include a soft magnetic layer of high permeability formed on their surfaces distal from the cell to improve the magnetic field still further. The fabrication of a cell with such thin lines is actually simplified as a result of the thinner depositions and eliminates the necessity of removing material by CMP during patterning and polishing, thereby producing uniform spacing between the lines and the cell free layer.
