A method for forming a semiconductor device, comprising forming: a first field-effect transistor, FET, device comprising a first semiconductor structure including a first source region, a first drain region, a first channel portion extending horizontally between said first source/drain regions, and a first gate structure at least partly wrapping around the first channel portion; a second FET device comprising a second semiconductor structure including a second source region, a second drain region, a second channel portion extending horizontally between said second source/drain regions, and a second gate structure at least partly wrapping around the second channel portion; wherein forming the first and second FET devices comprises: forming, on a semiconductor substrate, a fin comprising a first layer arranged on a second layer, wherein the first layer comprises a channel material forming the respective first and second semiconductor structures, and wherein the second layer comprises a sacrificial material; cutting the fin into a first stack and a second stack separated by a trench, each one of the first and second stacks comprising the first layer and the second layer; forming, in the trench, first spacers at sidewalls of the first and second stacks; forming a second spacer between the first spacers; forming a sacrificial gate extending across the first and second channel portions, the first spacers and the second spacer; recessing the sacrificial material at the source/drain regions; forming source/drain portions (130, 132) at the source/drain regions; removing the sacrificial gate; removing the first spacers; etching the sacrificial material of the first and second stacks to form at least partly released first and second channel portions of the channel material; and forming said first and second gate structures wrapping around the at least partly released first and second channel portions, the first gate structure of the first transistor device being separated from the second gate structure of the second transistor device by the second spacer. a first field-effect transistor, FET, device comprising a first semiconductor structure including a first source region, a first drain region, a first channel portion extending horizontally between said first source/drain regions, and a first gate structure at least partly wrapping around the first channel portion; a second FET device comprising a second semiconductor structure including a second source region, a second drain region, a second channel portion extending horizontally between said second source/drain regions, and a second gate structure at least partly wrapping around the second channel portion; wherein forming the first and second FET devices comprises: forming, on a semiconductor substrate, a fin comprising a first layer arranged on a second layer, wherein the first layer comprises a channel material forming the respective first and second semiconductor structures, and wherein the second layer comprises a sacrificial material; cutting the fin into a first stack and a second stack separated by a trench, each one of the first and second stacks comprising the first layer and the second layer; forming, in the trench, first spacers at sidewalls of the first and second stacks; forming a second spacer between the first spacers; forming a sacrificial gate extending across the first and second channel portions, the first spacers and the second spacer; recessing the sacrificial material at the source/drain regions; forming source/drain portions (130, 132) at the source/drain regions; removing the sacrificial gate; removing the first spacers; etching the sacrificial material of the first and second stacks to form at least partly released first and second channel portions of the channel material; and forming said first and second gate structures wrapping around the at least partly released first and second channel portions, the first gate structure of the first transistor device being separated from the second gate structure of the second transistor device by the second spacer. forming, on a semiconductor substrate, a fin comprising a first layer arranged on a second layer, wherein the first layer comprises a channel material forming the respective first and second semiconductor structures, and wherein the second layer comprises a sacrificial material; cutting the fin into a first stack and a second stack separated by a trench, each one of the first and second stacks comprising the first layer and the second layer; forming, in the trench, first spacers at sidewalls of the first and second stacks; forming a second spacer between the first spacers; forming a sacrificial gate extending across the first and second channel portions, the first spacers and the second spacer; recessing the sacrificial material at the source/drain regions; forming source/drain portions (130, 132) at the source/drain regions; removing the sacrificial gate; removing the first spacers; etching the sacrificial material of the first and second stacks to form at least partly released first and second channel portions of the channel material; and forming said first and second gate structures wrapping around the at least partly released first and second channel portions, the first gate structure of the first transistor device being separated from the second gate structure of the second transistor device by the second spacer.