Method for forming doped p-type gate with anti-reflection layer

Abstract

A method for forming doped p-type gate is disclosed as the following description. The method includes that, firstly, a semiconductor substrate is provided. The semiconductor substrate is etched to form a concave portion as a shallow trench isolation. A first silicon dioxide is filled into the shallow trench isolation. A n-type well is formed into the semiconductor substrate. A silicon germanium layer, named as the doped p-type layer is formed on the surface of semiconductor substrate and the surface of shallow trench isolation. A silicon nitride layer, named as the anti-reflection layer is formed on the surface of silicon germanium layer. The portions of silicon nitride layer and the portions of silicon germanium layer are etched as a gate region. The source/drain extension is formed. A second silicon dioxide layer is deposited over the surface of semiconductor substrate and the surface of nitride layer. The second silicon dioxide layer is etched as a spacer beside the sidewall of gate region. A source/drain region is formed into the semiconductor substrate. The silicon nitride layer is removed. Finally, salicide region is formed into the source/drain region and upon the surface of silcion layer to complete the silicon gate structure.