A memory cell structure and controlling the memory operation are simplified, and the cost of production is decreased lower than ever before. A semiconductor nonvolatile memory comprises a transistor including a gate electrode provided on a p-type semiconductor substrate via a gate insulating film, and a source region and a drain region, which are a pair of n-type impurity diffusion regions in the surface layer region of the semiconductor substrate at positions sandwiching the gate electrodes therebetween, and a first resistance-varying portion and a second resistance-varying portion which are the regions sandwiched by the source region, drain region and channel-forming region, and where the n-type impurity concentration is lower than those in the source region and in the drain region.