Patent ID: 7825457

Claim:
A semiconductor device comprising: a semiconductor substrate; a high concentration diffusion region formed in the semiconductor substrate and comprising first impurities implanted in the semiconductor substrate to a first depth from an upper face of the semiconductor substrate, the high concentration diffusion region having a first width measured orthogonal to the first depth thereof; a first low concentration diffusion region formed only under the high concentration diffusion region and comprising the first impurities implanted at a lower concentration than the high concentration diffusion region, the first low concentration diffusion region comprising the lower concentration of the first impurities implanted in the semiconductor substrate to a second depth from the upper face of the semiconductor substrate, the first low concentration diffusion region having a second width measured orthogonal to the second depth thereof; a first bit line formed in the semiconductor substrate and including a source region and a drain region, the first bit line including the high concentration diffusion region and the first low concentration diffusion region; and second low concentration diffusion regions formed on each side of the high concentration diffusion region, the second low concentration diffusion regions each implanted to a third depth from the upper face of the semiconductor substrate, wherein the third depth is less than the first depth.