US 12,218,197 B2
Gate oxide of nanostructure transistor with increased corner thickness
Shu-Han Chen, Hsinchu (TW); Yi-Shao Li, Hsinchu (TW); Chun-Heng Chen, Hsinchu (TW); and Chi On Chui, Hsinchu (TW)
Assigned to TAIWAN SEMICONDUCTOR MANUFACTURING CO., LTD., Hsinchu (TW)
Filed by Taiwan Semiconductor Manufacturing Co., Ltd., Hsinchu (TW)
Filed on Aug. 3, 2023, as Appl. No. 18/364,995.
Application 18/364,995 is a division of application No. 17/369,452, filed on Jul. 7, 2021, granted, now 11,855,140.
Claims priority of provisional application 63/084,833, filed on Sep. 29, 2020.
Prior Publication US 2023/0378262 A1, Nov. 23, 2023
Int. Cl. H01L 29/06 (2006.01); H01L 29/423 (2006.01); H01L 29/78 (2006.01)
CPC H01L 29/0665 (2013.01) [H01L 29/42364 (2013.01); H01L 29/42392 (2013.01); H01L 29/785 (2013.01); H01L 2029/7858 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A device comprising:
a plurality of semiconductor strips, wherein higher ones of the plurality of semiconductor strips overlap corresponding lower ones of the plurality of semiconductor strips, and the plurality of semiconductor strips are vertically spaced apart from each other by spaces; and
a gate stack comprising:
a plurality of oxide layers, each wrapping around one of the plurality of semiconductor strips, wherein one of the plurality of oxide layers comprises:
a first portion having a first thickness, wherein the first portion is a horizontal portion on a top surface of a corresponding one of the plurality of semiconductor strips, and wherein the first thickness is measured in a direction perpendicular to the top surface; and
a second portion having a second thickness greater than the first thickness, wherein the second thickness is measured in a diagonal direction of the one of the plurality of semiconductor strips, wherein the second portion is a corner portion at a corner of the corresponding one of the plurality of semiconductor strips, and the corner portion comprises an inner surface contacting the one of the plurality of semiconductor strips, and an outer surface opposite to, and parallel to, the inner surface, wherein the inner surface forms an obtuse angle with the top surface.