Two-bit magnetoresistive random-access memory cell

A method of forming a two-bit spin orbit torque (SOT) MRAM cell, the method comprising:

• forming a second heavy metal layer;
• forming a magnetic tunnel junction (MTJ) stack that comprises:
• a second MTJ above the second heavy metal layer, the second MTJ having a second cross-sectional area;
• and
• a first MTJ in series with the second MTJ, the first MTJ having a first cross-sectional area, wherein the first cross-sectional area is different than the second cross-sectional area, and wherein the first MTJ shares a reference layer with the second MTJ;
• and
• forming a first heavy metal layer above the first MTJ, wherein:
• the first heavy metal layer is connected to a first word line and to a bit line through a first transistor;
• the second heavy metal layer is connected to a second word line and to the bit line through a second transistor;
• the first heavy metal layer is connected to a third word line and to a source line through a third transistor;
• and
• the second heavy metal layer is connected directly to the source line.

A method of programming a two-bit MRAM cell, the method comprising:

• receiving a write command to program a first bit in a two-bit MRAM cell that comprises a first magnetic tunnel junction (MTJ) in series with a second MTJ, wherein:
• an area of the first MTJ is different than an area of the second MTJ;
• the first MTJ is coupled to a first heavy metal layer;
• the first heavy metal layer is connected to a bit line using a first transistor;
• the first heavy metal layer is connected to a source line using a second transistor;
• the second MTJ is connected to a second heavy metal layer;
• the second heavy metal layer is connected to the bit line using a third transistor;
• and
• the second heavy metal layer is directly connected to the source line;
• determining that the first bit is to be stored in a particular MTJ, wherein the particular MTJ is one of the first MTJ or the second MTJ;
• and
• selectively activating one or more of the first, second, and third transistors to cause current to flow through a heavy metal layer that is associated with the particular MTJ.

A system for programming a two-bit MRAM cell, wherein the system comprises:

• an MRAM cell comprising a first magnetic tunnel junction (MTJ) in series with a second MTJ, wherein:
• an area of the first MTJ is different than an area of the second MTJ;
• the first MTJ is coupled to a first heavy metal layer;
• the first heavy metal layer is connected to a bit line using a first transistor;
• the first heavy metal layer is connected to a source line using a second transistor;
• the second MTJ is connected to a second heavy metal layer;
• the second heavy metal layer is connected to the bit line using a third transistor;
• and
• the second heavy metal layer is directly connected to the source line;
• and
• a processor configured to perform a method comprising:
• receiving a write command to program a first bit in the MRAM cell;
• determining that the first bit is to be stored in a particular MTJ, wherein the particular MTJ is one of the first MTJ or the second MTJ;
• and
• selectively activating one or more of the first, second, and third transistors to cause current to flow through a heavy metal layer that is associated with the particular MTJ.