Method of fabricating semiconductor device

A method comprising:

• forming a first hard mask (HM) layer over a material layer;
• forming a second HM layer over the first HM layer, wherein the second HM layer has a plurality of first trenches, parallel to each other, extending along a first direction;
• forming a patterned resist layer having a first line opening over the second HM layer, wherein the first line opening extends along a second direction, which is perpendicular to the first direction, and overlaps with respect to the plurality of the first trenches, wherein respective portions of the second HM layer are exposed within the first line opening;
• etching the first HM layer by using the pattern resist layer and the exposed respective portions of the second HM layer together as an etching mask to form a plurality of first square-hole type features in the first HM layer and a second trench in the first HM layer;
• filling in the second trench with a sacrificial layer, wherein filling in the second trench with the sacrificial layer includes:
• depositing the sacrificial layer to fully fill in the second trench and partially fill in the plurality of first square-hole type features;
• and
• removing the sacrificial layer from the plurality of first square-hole type features;
• and
• with the sacrificial layer filled in the second trench, etching the material layer through the plurality of first square-hole type features to form a plurality of second square-hole type features in the material layer.

A method comprising:

• forming a first hard mask (HM) layer over a material layer;
• forming a patterned second HM layer over the first HM layer, wherein the patterned second HM layer defines a first trench extending along a first direction;
• forming a patterned material layer over the patterned second HM layer, wherein the patterned material layer has a first line opening extending along a second direction, which is perpendicular to the first direction, the first line opening overlapping the first trench and exposing a portion of the patterned second HM layer, wherein the patterned material layer further includes a second line opening that overlaps the first trench;
• and
• etching the first HM layer by using the patterned material layer and the exposed portion of the patterned second HM layer as an etch mask together to form a first hole feature in the first HM layer, wherein etching the first HM layer by using the patterned material layer and the exposed portion of the patterned second HM layer as the etch mask includes etching the first HM layer through a first opening to form a second hole feature in the first HM layer and etching the first HM layer through a second opening to form a second trench in the first HM layer;
• forming a sacrificial layer in the first hole feature and the second trench such that the first hole feature is partially filled with the sacrificial layer and the second trench is fully filled with the sacrificial layer;
• removing the sacrificial layer from the first hole feature while the sacrificial layer remains in the second trench;
• and
• etching the material layer through the first hole feature to form a third hole feature while the sacrificial layer remains in the second trench.