Disclosed are structures including a gate-all-around field effect transistor (GAAFET) with air-gap inner spacers. The GAAFET includes a stack of nanoshapes that extend laterally between source/drain regions, a gate that wraps around a center portion of each nanoshape, and a gate sidewall spacer on external sidewalls of the gate. The GAAFET also includes air-gap inner spacers between the gate and the source/drain regions. Each air-gap inner spacer includes: two vertical sections within the gate sidewall spacer on opposing sides of the stack and adjacent to a source/drain region; and horizontal sections below the nanoshapes and extending laterally between the vertical sections. Also discloses are methods of forming the structures and the method include forming preliminary inner spacers in inner spacer cavities prior to source/drain region formation. After source/drain regions are formed, the preliminary inner spacers are removed and the cavities are sealed off, thereby forming the air-gap inner spacers.