Patent ID: 6897526

Claim:
A semiconductor device comprising a plurality of MOSFETs formed in a single crystal semiconductor substrate, each of the plurality of MOSFETs comprising: a source region and a drain region each including a first impurity; a channel forming region being formed between the source region and the drain region; and an impurity region including a second impurity having an opposite conductive type to the first impurity and being formed under the channel forming region and in the source region, wherein the impurity region is formed at a depth in a range of 20 to 150 nm from a surface of the single crystal semiconductor substrate, wherein the impurity region is not in contact with the drain region, and wherein a concentration of the second impurity in the channel forming region is from {fraction (1/100)} to {fraction (1/10)} of that in the impurity region formed under the channel forming region and in the source region.