Provided herein are methods of forming a metal oxide layer pattern on a substrate including providing a preliminary metal oxide layer on a substrate; etching the preliminary metal oxide layer to provide a preliminary metal oxide layer pattern, wherein the line width of the preliminary metal oxide layer pattern gradually increases in a vertically downward direction; and etching the preliminary metal oxide layer pattern to form a metal oxide layer pattern in a manner so as to decrease the line width of a lower portion of the preliminary metal oxide layer. The present invention also provides methods of manufacturing a semiconductor device including forming a metal oxide layer and a first conductive layer on a substrate; etching the metal oxide layer to provide a preliminary metal oxide layer pattern, wherein the line width of the preliminary metal oxide layer pattern gradually increase in a vertically downward direction; etching the first conductive layer to provide a first conductive layer pattern; and etching the preliminary metal oxide layer pattern to provide a metal oxide layer pattern in a manner so as to decrease the line width of a lower portion of the preliminary metal oxide layer pattern.