Thin film magnetic memory device capable of conducting stable data read and write operations

A thin film magnetic memory device, comprising:

• a plurality of memory cells for retaining storage data, wherein each of said memory cells includes
• an access gate selectively turned ON in data read operation, and
• a magnetic storage portion connected in series with said access gate, and having either a first electric resistance or a second electric resistance higher than said first electric resistance depending on said storage data, and
• said magnetic storage portion includes
• a first magnetic layer having a fixed magnetization direction,
• a second magnetic layer that is magnetized in a same direction as, or in a direction opposite to, that of said first magnetic layer depending on said storage data to be written, and
• a first insulating film formed between said first and second magnetic layers, said thin film magnetic memory device further comprising:
• a data line that is electrically coupled to the magnetic storage portion of a selected memory cell through a turned-ON access gate of said selected memory cell in data read operation, said selected memory cell being a memory cell selected from said plurality of memory cells for said data read operation;
• a reference data line for transmitting in said data read operation a read reference voltage for comparison with a voltage on said data line;
• and
• a plurality of dummy memory cells for producing said read reference voltage, each of said dummy memory cells being provided for every fixed set of said memory cells, wherein
• each of said dummy memory cells includes
• a dummy access gate selectively turned ON in said data read operation, and
• a plurality of dummy magnetic storage portions that are electrically coupled to said reference data line in response to turning-ON of said dummy access gate,
• each of said dummy magnetic storage portions includes
• a third magnetic layer that is magnetized in a fixed direction,
• a fourth magnetic layer that is magnetized either in a same direction as, or in a direction opposite to, that of said third magnetic layer, and
• a second insulating film formed between said third and fourth magnetic layers, and
• each of said dummy magnetic storage portions is connected in series with at least one of the remainder.

A thin film magnetic memory device, comprising:

• a plurality of magnetic memory cells for retaining storage data written by an applied magnetic field;
• and
• a dummy memory cell for generating a read reference voltage in data read operation, wherein
• each of said magnetic memory cells and said dummy memory cell include
• a magnetic storage portion having either a first electric resistance value or a second electric resistance value that is higher than said first electric resistance value depending on a level of said storage data, and
• an access gate connected in series with said magnetic storage portion, and selectively turned ON, said thin film magnetic memory device further comprising:
• a first data line that is electrically coupled to a magnetic memory cell selected from said plurality of magnetic memory cells in data read operation so that a data read current is supplied to said first data line;
• a second data line that is electrically coupled to said dummy memory cell in data read operation so that a data read current equal to that of said first data line is supplied to said second data line;
• a data read circuit for producing read data based on respective voltages on said first and second data lines;
• and
• a resistance adding circuit for adding a third electric resistance in series with said first data line, said third electric resistance being smaller than a difference between said first and second electric resistance values, wherein
• said magnetic storage portion in said dummy memory cell stores a data level corresponding to said second electric resistance value.