A method used in forming an array of elevationally-extending transistors comprises forming vertically-alternating tiers of insulating material and void space. Such method includes forming (a) individual longitudinally-aligned channel openings extending elevationally through the insulating-material tiers, and (b) horizontally-elongated trenches extending elevationally through the insulating-material tiers. The void-space tiers are filled with conductive material by flowing the conductive material or one or more precursors thereof through at least one of (a) and (b) to into the void-space tiers. After the filling, transistor channel material is formed in the individual channel openings along the insulating-material tiers and along the conductive material in the filled void-space tiers.