A method of forming a microelectronic device structure comprises exposing a silicon structure to an etching chemistry at a first bias voltage of greater than about 500 V to form at least one initial trench between sidewalls of features formed in the silicon structure. The method also comprises exposing at least the sidewalls of the features to the etching chemistry at a second bias voltage of less than about 100 V to remove material from the sidewalls to expand the at least one initial trench and form at least one broader trench without substantially reducing a height of the features. Related apparatuses and electronic systems are also disclosed.