Ion-implantation method in solid materials for implanting impurities

Claim 1

An ion-implantation method for implanting desired impurities selectively in a solid material, which comprises forming a blocking film on said solid material, and implanting said impurities in said solid material with said blocking film used as a shielding mask for ion implantation, wherein said blocking film is composed of a first blocking layer with bordering first side walls of decreasing thickness, formed on said solid material, and a second blocking layer with bordering second side walls of decreasing thickness, formed on the portion of said first blocking layer other than said first side walls, said first blocking layer having a smaller etching rate than that of said second blocking layer, and said decreasing thickness of said first side walls providing a gentler slope than said decreasing thickness of said second side walls.

Claim 7

A method for the production of a metal-oxide-semiconductor field effect transistor, which method comprises: (a) providing a semiconductor substrate of a first conductivity type; (b) forming an insulated gate on a portion of said substrate, said insulated gate having an upper surface and opposite sides; (c) implanting first impurity ions of a second conductivity type in said substrate at a low concentration enough to form lightly doped source/drain regions with the use of the insulated gate as a shielding mask for ion implantation, whereby at least one of the source and drain regions is formed in said substrate; (d) forming a first blocking layer over said substrate including over said upper surface and opposite sides of said insulated gate; (e) forming a second blocking layer over said first blocking layer, said second blocking layer having a greater etching rate than that of said first blocking layer; (f) anisotropically etching said first and second blocking layers to produce bordering first and second side walls of decreasing thicknesses, respectively, at the edge of said insulated gate, said second blocking layer remaining on the portion of said first blocking layer other than said first side walls, and said decreasing thickness of said first side walls providing a gentler slope than said decreasing thickness of said second side walls; and (g) implanting second impurity ions of a second conductivity type in said substrate at a high concentration enough to form highly doped source/drain regions with the use of the insulated gate and the first and second blocking layers as a shielding mask for the ion implantation.

Claim 8

A method for the production of a metal-oxide-semiconductor field effect transistor, which method comprises: (a) providing a semiconductor substrate of a first conductivity type; (b) forming an insulated gate on a portion of said substrate, said insulated gate having an upper surface and opposite sides; (c) implanting first impurity ions of a second conductivity type in said substrate at a low concentration enough to form lightly doped source/drain regions with the use of the insulated gate as a shielding mask for ion implantation, whereby at least one of the source and drain regions is formed in said substrate; (d) forming a first blocking layer over said substrate including over said upper surface and opposite sides of said insulated gate; (e) forming a second blocking layer over said first blocking layer, said second blocking layer having a greater etching rate than that of said first blocking layer; (f) anisotropically etching said first and second blocking layers to produce bordering first and second side walls of decreasing thicknesses, respectively, at the edge of said insulated gate, said second blocking layer remaining on the portion of said first blocking layer other than said first side walls, and said decreasing thickness of said first side walls providing a gentler slope than said decreasing thickness of said second side walls; and (g) implanting second impurity ions of a second conductivity type in said substrate at a high concentration enough to form highly doped source/drain regions with the use of the insulated gate and the first and second blocking layers as a shielding mask for the ion implantation.