Patent ID: 7462545

Claim:
A method for forming a semiconductor device comprising: providing a substrate; forming a gate structure on the substrate; removing a portion of the substrate, using the gate structure as a mask, to form an opening with a depth in the substrate beside both sides of the gate structure; forming a first dielectric barrier layer on the substrate exposed by the opening; forming a second dielectric barrier layer on sidewalls of the gate structure and the substrate underneath the gate structure; removing the first dielectric barrier layer not covered by the second dielectric barrier layer; forming a first semiconductive layer in the opening with a thickness, wherein the thickness is less than the depth; removing a portion of the second dielectric barrier layer higher than a surface of the first semiconductive layer; forming a second semiconductive layer in the opening; and forming a source region and a drain region in the second semiconductive layer and the first semiconductive layer beside both sides of the gate structure.