A method of forming a vertical transistor comprising a top source/drain region, a bottom source/drain region, a channel region vertically between the top and bottom source/drain regions, and a gate operatively laterally-adjacent the channel region comprises, in multiple time-spaced microwave annealing steps, microwave annealing at least the channel region. The multiple time-spaced microwave annealing steps reduce average concentration of elemental-form H in the channel region from what it was before start of the multiple time-spaced microwave annealing steps. The reduced average concentration of elemental-form H is 0.005 to less than 1 atomic percent. Structure embodiments are disclosed.