A method of making a semiconductor device includes forming a first polysilicon structure over a first portion of a substrate. The method further includes forming a first spacer on a sidewall of the first polysilicon structure, wherein the first spacer has a concave corner region between an upper portion and a lower portion. The method further includes forming a protective layer covering an entirety of the first spacer and the first polysilicon structure, wherein the protective layer has a first thickness over the concave corner region and a second thickness over the first polysilicon structure, and a difference between the first thickness and the second thickness is at most 10% of the second thickness.

A method of making a semiconductor device includes forming a first polysilicon structure over a first portion of a substrate. The method further includes forming a first spacer on a sidewall of the first polysilicon structure, wherein the first spacer has a concave corner region between an upper portion and a lower portion. The method further includes forming a protective layer covering an entirety of the first spacer and the first polysilicon structure, wherein the protective layer has a first thickness over the concave corner region and a second thickness over the first polysilicon structure, and a difference between the first thickness and the second thickness is at most 10% of the second thickness.

A method includes: forming a barrier layer in a substrate; depositing a first dielectric layer over the substrate; forming a patterned mask layer over the first dielectric layer; patterning the first dielectric layer into a first sublayer of a gate dielectric layer; converting at least part of the patterned mask layer into a second sublayer of the gate dielectric layer; depositing a second dielectric layer adjacent to the first and second sublayers to serve as a third sublayer of the gate dielectric layer; and depositing a gate electrode over the gate dielectric layer.

A method includes: forming a barrier layer in a substrate; depositing a first dielectric layer over the substrate; forming a patterned mask layer over the first dielectric layer; patterning the first dielectric layer into a first sublayer of a gate dielectric layer; converting at least part of the patterned mask layer into a second sublayer of the gate dielectric layer; depositing a second dielectric layer adjacent to the first and second sublayers to serve as a third sublayer of the gate dielectric layer; and depositing a gate electrode over the gate dielectric layer.

A semiconductor structure includes: a semiconductor substrate; a gate dielectric layer over the semiconductor substrate; and a gate electrode over the gate dielectric layer. The gate dielectric layer includes a first portion and a second portion thinner than the first portion, wherein the gate electrode is over the first portion and the second portion, and the first portion includes a third portion including nitrogen and enclosed by the first portion.

A semiconductor structure includes: a semiconductor substrate; a gate dielectric layer over the semiconductor substrate; and a gate electrode over the gate dielectric layer. The gate dielectric layer includes a first portion and a second portion thinner than the first portion, wherein the gate electrode is over the first portion and the second portion, and the first portion includes a third portion including nitrogen and enclosed by the first portion.

A manufacture includes a polysilicon structure over a portion of a substrate. The manufacture further includes a spacer on a sidewall of the polysilicon structure, wherein the spacer has a concave corner region between an upper portion and a lower portion, the spacer has an outer sidewall and an inner sidewall, and the inner sidewall is between the outer sidewall and the polysilicon structure. The manufacture further includes a protective layer exposing a portion of the outer sidewall of the spacer above the concave corner region, wherein the protective layer covers an entirety of the lower portion of the spacer, and the protective layer directly contacts the substrate.

A manufacture includes a polysilicon structure over a portion of a substrate. The manufacture further includes a spacer on a sidewall of the polysilicon structure, wherein the spacer has a concave corner region between an upper portion and a lower portion, the spacer has an outer sidewall and an inner sidewall, and the inner sidewall is between the outer sidewall and the polysilicon structure. The manufacture further includes a protective layer exposing a portion of the outer sidewall of the spacer above the concave corner region, wherein the protective layer covers an entirety of the lower portion of the spacer, and the protective layer directly contacts the substrate.