Patent ID: 6788568
Filing Date: 2004-09-07
Classification: G11C,H01L

Abstract:
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 another one of the plurality of dummy magnetic storage portions.