Semiconductor device and method of forming the same

A method of forming a semiconductor device, comprising:

• forming an isolation structure on a substrate;
• forming a gate structure on the substrate;
• forming a source region and a drain region both having a first conductivity type in a substrate beside the gate structure and the isolation structure, wherein the source region is approximate to the gate structure, and the drain region is approximate to the isolation structure;
• forming a conductive layer on the substrate, wherein the conductive layer extends from above the source region to above the isolation structure and is electrically connected to the source region,
• wherein the substrate comprises a first area and a second area, a border curvature of the source region in the second area is greater than a border curvature of the source region in the first area, and a width of the a portion of the conductive layer covering the isolation structure in the second area is greater than a width of another portion of the conductive layer covering the isolation structure in the first area.