An array of elevationally-extending strings of memory cells comprises a vertical stack of alternating insulative tiers and wordline tiers. The wordline tiers have terminal ends corresponding to control-gate regions of individual memory cells. The control-gate regions individually comprise part of a wordline in individual of the wordline tiers. A charge-blocking region of the individual memory cells extends elevationally along the individual control-gate regions. Charge-storage material of the individual memory cells extends elevationally along individual of the charge-blocking regions. Channel material extends elevationally along the vertical stack. Insulative charge-passage material is laterally between the channel material and the charge-storage material. Elevationally-extending walls laterally separate immediately-laterally-adjacent of the wordlines. The walls comprise laterally-outer insulative material and silicon-containing material spanning laterally between the laterally-outer insulative material. The silicon-containing material comprises at least 30 atomic percent of at least one of elemental-form silicon or a silicon-containing alloy. Other aspects, including method, are also disclosed.