US 9,812,582 B2
Semiconductor device
Shunpei Yamazaki, Setagaya (JP)
Assigned to Semiconductor Energy Laboratory Co., Ltd., Atsugi-shi, Kanagawa-ken (JP)
Filed by Semiconductor Energy Laboratory Co., Ltd., Atsugi-shi, Kanagawa-ken (JP)
Filed on Dec. 11, 2015, as Appl. No. 14/966,177.
Application 14/966,177 is a continuation of application No. 14/594,958, filed on Jan. 12, 2015, granted, now 9,214,566.
Application 14/594,958 is a continuation of application No. 14/264,311, filed on Apr. 29, 2014, granted, now 8,946,704, issued on Feb. 3, 2015.
Application 14/264,311 is a continuation of application No. 13/751,721, filed on Jan. 28, 2013, granted, now 8,723,176, issued on May 13, 2014.
Claims priority of application No. 2012-020510 (JP), filed on Feb. 2, 2012.
Prior Publication US 2016/0099353 A1, Apr. 7, 2016
Int. Cl. H01L 29/12 (2006.01); H01L 29/786 (2006.01); H01L 29/04 (2006.01); H01L 29/24 (2006.01)
CPC H01L 29/7869 (2013.01) [H01L 29/04 (2013.01); H01L 29/045 (2013.01); H01L 29/24 (2013.01); H01L 29/78693 (2013.01); H01L 29/78696 (2013.01)] 27 Claims
OG exemplary drawing
 
1. A semiconductor device comprising:
a first oxide film over an insulating surface;
a second oxide film over the first oxide film; and
a third oxide film over the second oxide film,
wherein the third oxide film is in contact with a side surface of the second oxide film,
wherein each of the first oxide film, the second oxide film, and the third oxide film comprises indium, gallium, and zinc,
wherein a gallium content is higher than an indium content in the third oxide film,
wherein the gallium content is higher than a zinc content in the third oxide film, and
wherein an indium content in the second oxide film is higher than the indium content in the third oxide film.