US 6,271,572 B1 · Multi-voltage level semiconductor device and its manufacture

Abstract

In a semiconductor device comprising a MOS transistor driven at a relatively low voltage and a MOS transistor driven at a relatively high voltage formed on the same semiconductor substrate, the MOS transistor driven at the relatively high voltage comprises: a first active region of a first conductivity type in the semiconductor substrate; a first gate oxide film formed on the first active region and having increased thickness at the edge regions thereof than in the central region thereof in the direction of current flow; and a first electrode formed on the first gate oxide film and doped at a relatively low concentration with an impurity of a second conductivity type which is opposite to the first conductivity type; and the MOS transistor driven at the relatively low voltage comprises: a second active region of a first conductivity type in the semiconductor substrate; a second gate oxide film formed on the second active region; and a second electrode formed on the second gate oxide film and doped at a relatively high concentration with an impurity of a second conductivity type. A multi-voltage level semiconductor device is provided whereby increases in the number of manufacturing steps can be restricted and decline in the performance of MOS transistors for use in low-voltage circuits can be suppressed.

Claims15

Dependent claims

A semiconductor device comprising a first MOS transistor driven at a first voltage and a second MOS transistor driven at a second voltage higher than the first voltage both formed on a same semiconductor substrate, wherein:

the second MOS transistor driven at said relatively high voltage comprises:
a first active region of a first conductivity type in said semiconductor substrate;
a first gate oxide film formed on said first active region;
and
a first electrode formed on said first gate oxide film and doped at a first concentration with an impurity of a second conductivity type which is opposite to the first conductivity type;
and
the first MOS transistor driven at said relatively low voltage comprises:
a second active region of a first conductivity type in said semiconductor substrate;
a second gate oxide film formed on said second active region;
and
a second electrode formed on said second gate oxide film and doped at a second concentration higher than the first concentration with an impurity of the second conductivity type.

8 more elements

the second MOS transistor driven at said relatively high voltage comprises:
a first active region of a first conductivity type in said semiconductor substrate;
a first gate oxide film formed on said first active region;
and
a first electrode formed on said first gate oxide film and doped at a first concentration with an impurity of a second conductivity type which is opposite to the first conductivity type;
and
the first MOS transistor driven at said relatively low voltage comprises:
a second active region of a first conductivity type in said semiconductor substrate;
a second gate oxide film formed on said second active region;
a second electrode formed on said second gate oxide film and doped at a second concentration higher than the first concentration with an impurity of the second conductivity type, and
source/drain regions comprising low concentration regions and high concentration regions, said low concentration regions being doped at a low concentration level with an impurity of the second conductivity type, and being formed in said second active region such as to overlap partially on the substrate surface with respective end portions of said second electrode;
and said high concentration regions doped at a higher level than said low concentration level formed in said second active region adjacent to said low-concentration regions on opposite sides of said second electrode;
and
the second MOS transistor driven at said second voltage further comprises:
a field insulating region surrounding said first active region;
and source/drain regions doped at the same low concentration level as said low concentration regions of said source/regions of said first MOS transistor with an impurity of the second conductivity type, which is formed between said field insulating film and said first electrode and overlaps on the substrate surface with respective end portions of the first electrode.

13 more elements

Dependencies are inferred from the claim text.

Multi-voltage level semiconductor device and its manufacture

Life of this patent

Multi-voltage level semiconductor device and its manufacture

Life of this patent

Abstract

Claims15