Method of fabricating a semiconductor device

Claim 1

A method of fabricating a semiconductor device having MOSFETs, comprising the steps of: forming an insulating film as a gate insulator on a semiconductor layer of a first conductivity type; forming a first conductive film on said insulating film; forming a buffer film on said first conductive film, said buffer film having openings in gate line regions of said buffer film; forming a second conductive film on said buffer film; etching said second conductive film into wiring shape to form upper portions of gate lines of said MOSFETs, said upper portions covering said openings of said buffer film functioned as an etch stop and having a width which is wider than that of said openings; implanting ions of a second conductivity type into said semiconductor layer using said paper portions of said gate lines as an implant mask to form sources and drains in said semiconductor layer; forming sidewall spacers on the sides of said upper portions of said gate lines; etching said buffer film using said upper portions of said gate lines and said sidewall spacers as an etching mask; and etching said first conductive film using said upper portions of said gate lines and said side spacers as an etching mask, thereby forming under portions of said gate lines.

Claim 2

A method of fabricating a semiconductor device having MOSFETs, comprising the steps of: forming an insulating film as a gate insulator on a semiconductor layer of a first conductivity type; forming a first conductive film on said insulating film; forming a buffer film on said first conductive film, said buffer film having openings in gate line regions of said buffer film; forming a second conductive film on said buffer film; etching said second conductive film into wiring shape to form upper portions of gate lines of said MOSFETs, said upper portions covering said openings of said buffer film functioned as an etch stop and having a width which is wider than that of said openings; implanting ions of a second conductivity type into said semiconductor layer using said paper portions of said gate lines as an implant mask to form sources and drains in said semiconductor layer; forming sidewall spacers on the sides of said upper portions of said gate lines; etching said buffer film using said upper portions of said gate lines and said sidewall spacers as an etching mask; and etching said first conductive film using said upper portions of said gate lines and said side spacers as an etching mask, thereby forming under portions of said gate lines.

Claim 11

A method of fabricating a semiconductor device having MOSFETs, comprising the steps of: forming an insulating film as a gate insulator on a semiconductor layer of a first conductivity type; forming a first conductive film on said insulating film; forming a buffer film on said first conductive film, said buffer film having openings in gate line regions of said buffer film; forming a second conductive film on said buffer film; etching said second conductive film into wiring shapes to form upper portions of gate lines of said MOSFETs, said upper portions covering said openings of said buffer film functioned as an etch stop and having a width which is wider than that of said openings; forming on said buffer layer an implant mask layer to cover source regions of said semiconductor layer; implanting ions of a second conductivity type into said semiconductor layer using said upper portions of said gate lines and said mask layer as an implant mask to form drains in said semiconductor layer; removing said mask layer from said buffer layer; forming sidewall spacers on the sides of said upper portions of said gate lines; and etching said buffer film using said upper portions of said gate lines and said sidewall spacers as an etching mask; etching said first conductive film using said upper portions of said gate lines and said sidewall spacers as an etching mask, thereby forming under portions of said gate lines; and implanting ions of a second conductivity type semiconductor layer using said upper portions of said gate lines and said sidewall spacers as an implant mask to form sources in said semiconductor layer and to reduce the resistance of said drains.

Claim 12

A method of fabricating a semiconductor device having MOSFETs, comprising the steps of: forming an insulating film as a gate insulator on a semiconductor layer of a first conductivity type; forming a first conductive film on said insulating film; forming a buffer film on said first conductive film, said buffer film having openings in gate line regions of said buffer film; forming a second conductive film on said buffer film; etching said second conductive film into wiring shapes to form upper portions of gate lines of said MOSFETs, said upper portions covering said openings of said buffer film functioned as an etch stop and having a width which is wider than that of said openings; forming on said buffer layer an implant mask layer to cover source regions of said semiconductor layer; implanting ions of a second conductivity type into said semiconductor layer using said upper portions of said gate lines and said mask layer as an implant mask to form drains in said semiconductor layer; removing said mask layer from said buffer layer; forming sidewall spacers on the sides of said upper portions of said gate lines; and etching said buffer film using said upper portions of said gate lines and said sidewall spacers as an etching mask; etching said first conductive film using said upper portions of said gate lines and said sidewall spacers as an etching mask, thereby forming under portions of said gate lines; and implanting ions of a second conductivity type semiconductor layer using said upper portions of said gate lines and said sidewall spacers as an implant mask to form sources in said semiconductor layer and to reduce the resistance of said drains.

Claim 13

A method of fabricating a semiconductor device having MOSFETs, comprising the steps of: forming an insulating film on a semiconductor layer of a first conductivity type; forming a first conductive film on said insulating film; forming a buffer film on said first conductive film, said buffer film having openings in gate line regions of said buffer film; forming a second conductive film on said buffer film; etching said second conductive film into wiring shape to form upper portions of said gate lines, said upper portions covering said openings of said buffer film functioned as an etch stop and having a width which is wider than that of said openings; implanting ions of a second conductivity type into said semiconductor layer using said upper portions of said gate lines as an implant mask to form sources and drains in said semiconductor layer, said ions are implanted into said semiconductor layer in an oblique direction; etching said buffer film using said upper portions of said gate lines as an etching mask; and etching said first conductive film using said upper portions of said gate lines as an etching mask, thereby forming under portions of said gate lines.

Claim 14

A method of fabricating a semiconductor device having MOSFETs, comprising the steps of: forming an insulating film on a semiconductor layer of a first conductivity type; forming a first conductive film on said insulating film; forming a buffer film on said first conductive film, said buffer film having openings in gate line regions of said buffer film; forming a second conductive film on said buffer film; etching said second conductive film into wiring shape to form upper portions of said gate lines, said upper portions covering said openings of said buffer film functioned as an etch stop and having a width which is wider than that of said openings; implanting ions of a second conductivity type into said semiconductor layer using said upper portions of said gate lines as an implant mask to form sources and drains in said semiconductor layer, said ions are implanted into said semiconductor layer in an oblique direction; etching said buffer film using said upper portions of said gate lines as an etching mask; and etching said first conductive film using said upper portions of said gate lines as an etching mask, thereby forming under portions of said gate lines.

Claim 21

A method of fabricating a semiconductor device having MOSFETs, comprising the steps of: forming an insulating film on a semiconductor layer of a first conductivity type; forming a first conductive film on said insulating film; forming a buffer film on said first conductive film, said buffer film having openings in gate line regions of said buffer film; forming a second conductive film on said buffer film; etching said second conductive film into wiring shapes to form upper portions of said gate lines, said upper portions covering said openings of said buffer film functioned as an etch stop and having a width which is wider than that of said openings; implanting ions of a second conductivity type into said semiconductor layer using said upper portions of said gate lines as an implant mask to form sources and drains in said semiconductor layer; removing said buffer film from said first conductive film; forming sidewall spacers on the sides of said upper portions of said gate lines; and etching said first conductive film using said upper portions of said gate lines and said side spacers as an etching mask, thereby forming under portions of said gate lines.

Claim 22

A method of fabricating a semiconductor device having MOSFETs, comprising the steps of: forming an insulating film on a semiconductor layer of a first conductivity type; forming a first conductive film on said insulating film; forming a buffer film on said first conductive film, said buffer film having openings in gate line regions of said buffer film; forming a second conductive film on said buffer film; etching said second conductive film into wiring shapes to form upper portions of said gate lines, said upper portions covering said openings of said buffer film functioned as an etch stop and having a width which is wider than that of said openings; implanting ions of a second conductivity type into said semiconductor layer using said upper portions of said gate lines as an implant mask to form sources and drains in said semiconductor layer; removing said buffer film from said first conductive film; forming sidewall spacers on the sides of said upper portions of said gate lines; and etching said first conductive film using said upper portions of said gate lines and said side spacers as an etching mask, thereby forming under portions of said gate lines.