Method of forming buried contact between polysilicon gate and diffusion area

Claim 1

A method for effecting electrical contact between the gate of a transistor device formed at the surface of a substrate and a diffusion region of a first conductivity type located in the surface of the substrate remote from the transistor device, said method comprising the steps: (a) forming a thin insulative layer on the surface of the substrate; (b) forming a polysilicon gate on said thin insulative layer; (c) istropically etching the thin insulative layer to expose the surface of the substrate; (d) isotropically depositing a polysilicon interconnect layer which contacts an edge of the gate and the surface of the substrate exposed in said step of isotropically etching; (e) anisotropically etching said polysilicon interconnect layer to remove same from a portion of said surface of the substrate separated from the gate and exposed in said step of isotropically etching, thereby to produce from said polysilicon interconnect layer a polysilicon interconnect structure disposed against the gate and contacting the surface of the substrate, the surface of the substrate contacted by said polysilicon interconnect layer being remote from the diffusion region and defining a surface current pathway interface; (f) insulating the exposed surface of said polysilicon interconnect structure; (g) implanting ions of the first conductivity type to introduce an implant region remote from said gate and to produce ions of the first conductivity type in said gate; and (h) inducing migration of ions of the first conductivity type from the implantation region and from the gate through said polysilicon interconnect structure into the substrate to form in the substrate below said surfaces first and second migration regions of the first conductivity type, said migration regions extending laterally to from a buried current pathway interface having a substantial area of connection between said first and second migration regions.

Claim 2

A method for effecting electrical contact between the gate of a transistor device formed at the surface of a substrate and a diffusion region of a first conductivity type located in the surface of the substrate remote from the transistor device, said method comprising the steps: (a) forming a thin insulative layer on the surface of the substrate; (b) forming a polysilicon gate on said thin insulative layer; (c) istropically etching the thin insulative layer to expose the surface of the substrate; (d) isotropically depositing a polysilicon interconnect layer which contacts an edge of the gate and the surface of the substrate exposed in said step of isotropically etching; (e) anisotropically etching said polysilicon interconnect layer to remove same from a portion of said surface of the substrate separated from the gate and exposed in said step of isotropically etching, thereby to produce from said polysilicon interconnect layer a polysilicon interconnect structure disposed against the gate and contacting the surface of the substrate, the surface of the substrate contacted by said polysilicon interconnect layer being remote from the diffusion region and defining a surface current pathway interface; (f) insulating the exposed surface of said polysilicon interconnect structure; (g) implanting ions of the first conductivity type to introduce an implant region remote from said gate and to produce ions of the first conductivity type in said gate; and (h) inducing migration of ions of the first conductivity type from the implantation region and from the gate through said polysilicon interconnect structure into the substrate to form in the substrate below said surfaces first and second migration regions of the first conductivity type, said migration regions extending laterally to from a buried current pathway interface having a substantial area of connection between said first and second migration regions.