Abstract: A method for forming a semiconductor structure includes: forming a first gate structure in a predetermined low-potential region of a substrate and a second gate structure in a predetermined high-potential region of the substrate; sequentially forming a first dielectric layer and a second dielectric layer covering the first gate structure and the second gate structure; forming a portion of a third dielectric layer along sidewalls of the second gate structure and on the second dielectric layer; and etching the first dielectric layer and the second dielectric layer with the portion of the third dielectric layer as an etching hard mask to form a first composite spacer covering sidewalls of the first gate structure, and a second composite spacer covering the sidewalls of the second gate structure, wherein a width of the first composite spacer is less than a width of the second composite spacer.

Abstract: A method for forming a semiconductor structure includes: forming a first gate structure in a predetermined low-potential region of a substrate and a second gate structure in a predetermined high-potential region of the substrate; sequentially forming a first dielectric layer and a second dielectric layer covering the first gate structure and the second gate structure; forming a portion of a third dielectric layer along sidewalls of the second gate structure and on the second dielectric layer; and etching the first dielectric layer and the second dielectric layer with the portion of the third dielectric layer as an etching hard mask to form a first composite spacer covering sidewalls of the first gate structure, and a second composite spacer covering the sidewalls of the second gate structure, wherein a width of the first composite spacer is less than a width of the second composite spacer.

Abstract: A high-voltage semiconductor device is provided. The device includes a semiconductor substrate, a gate dielectric layer, a T-shaped gate, a dielectric neck support, an etch stop feature, a pair of drift regions, and a pair of source/drain regions. The semiconductor substrate has a high-voltage well region. The gate dielectric layer is on the semiconductor substrate. The T-shaped gate is on the gate dielectric layer. The T-shaped gate includes overhangs that extend beyond the neck portion of the T-shaped gate. The dielectric neck support is disposed underneath the overhangs of the T-shaped gate. The etch stop feature is disposed underneath the dielectric neck support. The drift regions are disposed on opposite sides of the T-shaped gate in the high-voltage well region. The source/drain regions are disposed in the pair of drift regions.

Abstract: A high-voltage semiconductor device is provided. The device includes a semiconductor substrate including a high-voltage well region. The device further includes a gate dielectric structure and a gate. The gate dielectric structure includes a first dielectric layer over the high-voltage well region and a second dielectric layer over the first dielectric layer. The second dielectric layer has a U-shaped or ring-shaped contour as viewed from a top-view aspect, so as to form an opening exposing the first dielectric layer. The gate is disposed over the second dielectric layer and extends onto the exposed first dielectric layer via the opening. The device further includes a drift doping region in the high-voltage well region and a source/drain doping region in the drift doping region. A method for fabricating the high-voltage semiconductor device is also provided.