Well implant through dummy gate oxide in gate-last process

A method for making a field-effect transistor, comprising:

• forming a dummy oxide layer on a surface of a substrate having a semiconductor material;
• performing a first implant process to form a doped well region in the substrate;
• performing a second implant process through the dummy oxide layer to form a retrograde well in a first region of the doped well region of the substrate;
• performing a third implant process through the dummy oxide layer to form a pocket in a second region of the doped well region of the substrate, the second region being disposed over the first region;
• after performing the third implant process, depositing a polycrystalline (polysilicon) layer on the dummy oxide layer;
• patterning the polysilicon layer and the dummy oxide layer to form a dummy poly gate of the transistor;
• forming a source and a drain of the transistor in the substrate;
• and
• replacing the dummy poly gate with a metal gate.

A method of fabricating a field-effect transistor comprising:

• performing a pocket implantation to a semiconductor substrate;
• thereafter forming a polysilicon layer on the semiconductor substrate;
• and
• patterning the polysilicon layer to form a polysilicon gate,
• wherein performing the pocket implantation to the semiconductor substrate forms a pocket region in the substrate, the method further comprising forming a source and a drain in the semiconductor substrate such that the pocket region extends from the source to the drain.