A method for forming a field-effect transistor device (100; 200), the method comprising: forming a fin structure (1010; 2010) comprising a layer stack comprising channel layers (1004; 2004) and non-channel layers (1022, 1006; 2022) alternating the channel layers (1004; 2004), the fin structure (1010; 2020) comprising a first fin part (1010s; 2010s), a second fin part (1010d; 2010d) and a third fin part (1010c; 2010c) intermediate the first and second fin parts; etching each of the first and second fin parts (1010s, 1010d; 2010s, 2010d) laterally from each of first and second opposite sides (1010a, 1010b; 2010a, 2010b) of the fin structure (1010; 2010) such that a set of source cavities (1048; 2048) extending through the first fin part is formed in a first set of layers of the layer stack, and such that a set of drain cavities (1048; 2048) extending through the second fin part is formed in the first set of layers of the layer stack; filling the source and drain cavities (1048; 2048) with a dummy material; while masking the fin structure from the second side (1010b; 2010b): - removing the dummy material from the source and drain cavities by etching from the first side (1010a; 2010a), and - subsequently, forming a source body and a drain body (1120s, 1120d; 2120s, 2120d), each comprising a respective common body portion along the first side (1010a; 2010a) and a set of prongs protruding from the respective common body portion into the source and drain cavities, respectively, and abutting the channel layers (1004; 2004); and while masking the fin structure from the first side (1010a; 2010a): - etching the third fin part (1010c; 2010c) laterally from the second side (1010b; 2010b) such that a set of gate cavities (1060; 2060) extending through the third fin part is formed in a second set of layers defined by non-channel layers of the layer stack, the second set of layers being different from the first set of layers, and - subsequently, forming a gate body (1140; 2140) comprising a common gate body portion (1142; 2142) along the second side and a set of gate prongs (1144; 2144) protruding from the common gate body portion into the gate cavities (1060; 2060). forming a fin structure (1010; 2010) comprising a layer stack comprising channel layers (1004; 2004) and non-channel layers (1022, 1006; 2022) alternating the channel layers (1004; 2004), the fin structure (1010; 2020) comprising a first fin part (1010s; 2010s), a second fin part (1010d; 2010d) and a third fin part (1010c; 2010c) intermediate the first and second fin parts; etching each of the first and second fin parts (1010s, 1010d; 2010s, 2010d) laterally from each of first and second opposite sides (1010a, 1010b; 2010a, 2010b) of the fin structure (1010; 2010) such that a set of source cavities (1048; 2048) extending through the first fin part is formed in a first set of layers of the layer stack, and such that a set of drain cavities (1048; 2048) extending through the second fin part is formed in the first set of layers of the layer stack; filling the source and drain cavities (1048; 2048) with a dummy material; while masking the fin structure from the second side (1010b; 2010b): - removing the dummy material from the source and drain cavities by etching from the first side (1010a; 2010a), and - subsequently, forming a source body and a drain body (1120s, 1120d; 2120s, 2120d), each comprising a respective common body portion along the first side (1010a; 2010a) and a set of prongs protruding from the respective common body portion into the source and drain cavities, respectively, and abutting the channel layers (1004; 2004); and - removing the dummy material from the source and drain cavities by etching from the first side (1010a; 2010a), and - subsequently, forming a source body and a drain body (1120s, 1120d; 2120s, 2120d), each comprising a respective common body portion along the first side (1010a; 2010a) and a set of prongs protruding from the respective common body portion into the source and drain cavities, respectively, and abutting the channel layers (1004; 2004); and while masking the fin structure from the first side (1010a; 2010a): - etching the third fin part (1010c; 2010c) laterally from the second side (1010b; 2010b) such that a set of gate cavities (1060; 2060) extending through the third fin part is formed in a second set of layers defined by non-channel layers of the layer stack, the second set of layers being different from the first set of layers, and - subsequently, forming a gate body (1140; 2140) comprising a common gate body portion (1142; 2142) along the second side and a set of gate prongs (1144; 2144) protruding from the common gate body portion into the gate cavities (1060; 2060). - etching the third fin part (1010c; 2010c) laterally from the second side (1010b; 2010b) such that a set of gate cavities (1060; 2060) extending through the third fin part is formed in a second set of layers defined by non-channel layers of the layer stack, the second set of layers being different from the first set of layers, and - subsequently, forming a gate body (1140; 2140) comprising a common gate body portion (1142; 2142) along the second side and a set of gate prongs (1144; 2144) protruding from the common gate body portion into the gate cavities (1060; 2060).