US 5,962,894 A · Trench transistor with metal spacers

Abstract

An IGFET with a gate electrode and metal spacers in a trench is disclosed. The IGFET includes a trench with opposing sidewalls and a bottom surface in a semiconductor substrate, metal spacers adjacent to the sidewalls and the bottom surface, a gate insulator on the bottom surface between the metal spacers, protective insulators on the metal spacers, a gate electrode on the gate insulator and protective insulators, and a source and drain adjacent to the bottom surface. A method of forming the IGFET includes implanting a doped layer into the substrate, etching completely through the doped layer and partially through the substrate to form the trench and split the doped layer into source and drain regions, applying a high-temperature anneal to diffuse the source and drain regions beneath the bottom surface, depositing a blanket layer of conductive metal over the substrate and applying an anisotropic etch to form the metal spacers, depositing a continuous insulative layer over the substrate to provide the gate insulator and the protective insulators, depositing a blanket layer of gate electrode material over the substrate, and polishing the gate electrode material so that the gate electrode is substantially aligned with a top surface of the substrate. Advantageously, the channel length is significantly smaller than the trench length, and the metal spacers reduce the parasitic resistance of lightly doped source and drain regions.

Claims40

Dependent claims

An IGFET, comprising:

a substrate including a trench;
metal spacers in the trench;
a gate insulator on a bottom surface of the trench;
a gate electrode on the gate insulator and electrically isolated from the metal spacers;
and
a source and a drain in the substrate and adjacent to the bottom surface.

3 more elements

An IGFET, comprising:

a semiconductor substrate doped a first conductivity type including a trench extending beneath a top surface, wherein the trench includes first and second opposing sidewalls and a bottom surface, and the bottom surface includes a central portion between and spaced from the sidewalls;
first and second metal spacers on the bottom surface outside the central portion and adjacent to the sidewalls;
first and second protective insulators on sides of the first and second metal spacers, respectively, opposite to the first and second sidewalls, respectively;
a gate insulator on the central portion and adjacent to the protective insulators;
a gate electrode on the gate insulator, and on sides of the protective insulators opposite the metal spacers, wherein the gate electrode is spaced from and electrically isolated from the metal spacers and the substrate;
a source doped a second conductivity type in the substrate, wherein the source extends between the top and bottom surfaces, and the source contacts the first metal spacer at the first sidewall and at the bottom surface;
a drain doped the second conductivity type in the substrate, wherein the drain extends between the top and bottom surfaces, and the drain contacts the second metal spacer at the second sidewall and at the bottom surface;
and
a channel doped the first conductivity type in the substrate, wherein the channel extends between the source and the drain and is adjacent to the central portion.

6 more elements

Dependencies are inferred from the claim text.

Trench transistor with metal spacers

Life of this patent

Trench transistor with metal spacers

Life of this patent

Abstract

Claims40