Abstract: According to an aspect there is provided a patterning method comprising: over a lower pattern memorization layer, forming a pattern of first upper blocks, then an upper pattern memorization layer and then a pattern of second upper blocks; thereafter patterning upper trenches in the upper pattern memorization layer using lithography and etching, and forming spacer lines along sidewalls of the upper trenches to define spacer-provided upper trenches, at least a subset being interrupted by a respective first upper block; patterning first lower trenches in the lower pattern memorization layer by etching the spacer-provided upper trenches into the lower pattern memorization layer, at least a subset of the first lower trenches being interrupted by a lower pattern memorization layer portion preserved at a location defined by a respective one of the first upper blocks; thereafter, forming an auxiliary trench mask stack and patterning auxiliary trenches therein using lithography and etching; and thereafter, patterni