Method of fabricating a semiconductor device

A method for fabricating a semiconductor device, comprising the steps of:

• sequentially forming a plurality of gate insulating layers and a plurality of gates over a semiconductor substrate of a first conductivity type;
• forming a first active region of a second conductivity type in the semiconductor substrate by ion-implanting a first impurity of the second conductivity type at a first dose, using the plurality of gates as a mask;
• forming sidewall spacers of an insulating material on the sidewalls of the plurality of gates;
• forming a second active region of the second conductivity type in the semiconductor substrate by masking a portion of the first active region and ion-implanting a second impurity of the second conductivity type at a second dose higher than the first dose;
• and
• forming a first silicide layer over exposed portions of the first and second active regions.

A semiconductor device, comprising:

• a plurality of gate insulating layers formed over a semiconductor substrate of a first conductive type;
• a plurality of gates formed over the gate insulating layers;
• a first active region formed in the semiconductor substrate between the plurality of gates, the first active region comprising a first impurity layer of a second conductivity type having a first impurity concentration, and a second impurity layer of the second conductivity type having a second impurity concentration higher than the first impurity concentration;
• a second active region, narrower than the first active region, formed in the semiconductor substrate between the plurality of gates, the second active region comprising a third impurity layer of the second conductivity type having a third impurity concentration substantially the same as the first impurity concentration;
• and
• a first silicide layer formed over the first active region and the second active region.