Gate-all-around nanowire device and method for manufacturing such a device

A method of fabricating a semiconductor device, the method comprising:

• providing a semiconductor substrate having a main surface;
• forming on the main surface a vertical stack comprising nanowires formed of a first material and interlayer nanowires formed of an interlayer material different from the first material, wherein the nanowires and the interlayer nanowires alternate in a vertical direction and laterally extend in a longitudinal direction parallel to the main surface, wherein the nanowires have two ends at opposite sides of the nanowire and an inner part therebetween in the longitudinal direction, wherein the inner part has two sides and an outer part at each side in the longitudinal direction, and wherein the nanowires include a first conductivity type nanowire and an intermediate second conductivity type nanowire configured to be converted to a second conductivity type nanowire;
• selectively providing at at least one of two ends of the intermediate second conductivity type nanowire a conversion material different from the first material and configured to convert the first material of the intermediate second conductivity type nanowire into a second material;
• removing the interlayer nanowires;
• after removing, converting the first material of at least one of the two outer parts of the intermediate second conductivity type nanowire into the second material, thereby converting the intermediate second conductivity type nanowire into the second conductivity type nanowire, wherein the first material of the first conductivity type nanowire remains unconverted;
• and
• forming a shared gate structure around the first conductivity type and second conductitivy type nanowires.