Semiconductor device and fabrication method for the same

A semiconductor device comprising:

• a plurality of bit lines formed in stripes in a semiconductor substrate of a first conductivity type, each of the bit lines being a diffusion layer of an impurity of a second conductivity type;
• a plurality of gate insulation films formed on regions of the semiconductor substrate between the plurality of bit lines;
• a plurality of word lines formed on the semiconductor substrate via the gate insulating films, the word lines extending in a direction intersecting with the plurality of bit lines;
• and
• a plurality of bit line isolation diffusion layers formed in regions of the semiconductor substrate between the plurality of word lines, each of the bit line isolation diffusion layers being a diffusion layer of an impurity of the first conductivity type and including a first diffusion suppressor for suppressing diffusion of an impurity,
• wherein the first diffusion suppressor is a different element from the impurity of the first conductivity type, and
• the first diffusion suppressor is formed shallower than the impurity of the first conductivity type.