text: A tunnel magnetoresistance device has a structure in which a tunnel insulating film is sandwiched by two ferromagnetic layers. When the tunnel magnetoresistance device is applied to a magnetoresistive random access memory (MRAM), one of the two ferromagnetic layers configuring the tunnel magnetoresistance device has a magnetization whose direction is fixed, and serves as a fixed layer (pinned layer). The other ferromagnetic layer is such that a magnetization is variable, and serves as a storage layer. Accordingly, the MRAM can store nonvolatile data and write and read data in a time equal to or less than 10 nanoseconds (ns). In addition, the MRAM can rewrite data more than 1015 times.
  A spin injection magnetization switching method has been proposed as a method of writing information to each tunnel magnetoresistance device of an MRAM. The spin injection magnetization switching method is to reverse the magnetization of a storage layer of a tunnel magnetoresistance device of an MRAM by injecting spin-polarized electrons (or spin injection current) into the tunnel magnetoresistance device of the MRAM. The magnitude of spin injection current needed to write information to the tunnel magnetoresistance device of the MRAM is reduced with the miniaturization of the tunnel magnetoresistance device of the MRAMs. Thus, the spin injection magnetization switching method is promising as a method of writing information to each tunnel magnetoresistance device of an MRAM.
  However, in order to write information to each tunnel magnetoresistance device of an MRAM using the spin injection magnetization switching method, it is necessary to apply electric-current bidirectionally to the tunnel magnetoresistance device of the MRAM. In a cross-point type structure in which each tunnel magnetoresistance device of the MRAM and a diode are connected in series between a bit line and a word line, electric-current can not be applied bidirectionally.
  Even in a spin transistor having a tunnel magnetoresistance device at least at one of a source electrode and a drain electrode, electric-current is bidirectionally applied thereto at the writing of information thereto. Thus, a peripheral circuit is complicated.