US 12,249,649 B2
Semiconductor device
Cheng-Han Wu, Hsinchu (TW); Hsin-Yu Chen, Nantou County (TW); Chun-Hao Lin, Kaohsiung (TW); Shou-Wei Hsieh, Hsinchu (TW); Chih-Ming Su, Tainan (TW); Yi-Ren Chen, Kaohsiung (TW); and Yuan-Ting Chuang, Yilan County (TW)
Assigned to UNITED MICROELECTRONICS CORP., Hsin-Chu (TW)
Filed by UNITED MICROELECTRONICS CORP., Hsin-Chu (TW)
Filed on Mar. 22, 2021, as Appl. No. 17/207,751.
Application 17/207,751 is a continuation of application No. 16/252,715, filed on Jan. 21, 2019, granted, now 10,991,824.
Claims priority of application No. 107146345 (TW), filed on Dec. 21, 2018.
Prior Publication US 2021/0210628 A1, Jul. 8, 2021
Int. Cl. H01L 29/78 (2006.01); H01L 21/762 (2006.01); H01L 29/417 (2006.01)
CPC H01L 29/785 (2013.01) [H01L 21/76224 (2013.01); H01L 29/41791 (2013.01); H01L 29/7831 (2013.01)] 18 Claims
OG exemplary drawing
 
1. A semiconductor device, comprising:
a first gate structure on a substrate, wherein the first gate structure comprises:
a U-shaped high-k dielectric layer;
a U-shaped work function metal layer; and
a low-resistance metal layer;
two spacers disposed on two sides of the U-shaped high-k dielectric layer respectively;
a first epitaxial layer on one side of the first gate structure; and
a second epitaxial layer on another side of the first gate structure, wherein the first epitaxial layer and the second epitaxial layer comprise different sizes and top surfaces of the first epitaxial layer and the second epitaxial layer are coplanar, and wherein a portion of the first epitaxial layer and a portion of the second epitaxial layer are disposed right under the spacers, wherein viewed from a cross section, the cross section of the first epitaxial layer is a major segment of a circular shape, and a width of the first epitaxial layer is larger than a depth of the first epitaxial layer, and the cross section of the second epitaxial layer is a major segment of an ellipse shape, wherein the second epitaxial layer has a flat top surface, and a lower portion of the second epitaxial layer has an elliptical profile, and wherein a short axis through the center of the ellipse shape of the second epitaxial layer is less than a diameter of the circular shape of the first epitaxial layer.