Chapter 2 discusses multiple-junction devices made of thin-film of silicon deposited from a vapor phase. This technology—which combines the advantages of silicon-based technologies (non-toxicity, availability) and of thin-films technologies (sparse use of materials, upscalibility, flexibility)—is unbeatable in terms of price per m2 and has therefore attracted a lot of attention in the race to a massive integration of PV in the world electricity mix. The basics of the technology are reviewed in a first part, including the historical development of amorphous and microcrystalline silicon and alloys, and the essential challenges of multi-junction integration; a second part gathers the most relevant results in terms of efficiency and tackles the recent developments which brought novel advances to the technology, as well as the most promising routes for further improvements.