Nanowire channel field effect device and method for manufacturing the same

A method of manufacturing a semiconductor device, comprising:

• forming a first insulating film on a semiconductor substrate;
• forming a first semiconductor layer on the first insulating film, and forming a mask on an upper face of the first semiconductor layer, the first semiconductor layer including:
• a first region having:
• a first side face and a second side face opposite to the first side face, and
• a first width along a first direction from the first side face to the second side face;
• a second region having a second width along a second direction parallel to the first direction, the second width being greater than the first width;
• and
• a third region having a third width along a third direction parallel to the first direction, the third width being greater than the first width,
• at least one of the second and third regions being connected to the first region, and
• the first, second, and third regions being covered by the mask;
• performing, using the mask, a first ion implantation to implant ions into substantially the entire first region through the first and second side faces of the first region of the first semiconductor layer to transform the first region to an amorphous semiconductor;
• performing, after the first ion implantation is performed, a first heat treatment including:
• crystallizing the first region of the first semiconductor layer, with crystals in the at least one of the second and third regions being seed crystals;
• forming, after the mask is removed, a gate insulating film at least on the first and second side faces of the first region of the first semiconductor layer;
• forming a gate electrode on the gate insulating film;
• forming gate sidewalls made of an insulating material on side faces of the gate electrode on sides of the second and third regions;
• and
• performing a second ion implantation at least into the second and third regions of the first semiconductor layer.