Semiconductor device with annular semiconductor fin and method for preparing the same

A method for preparing a semiconductor device, comprising:

• forming a ring structure over a semiconductor substrate;
• etching the semiconductor substrate by using the ring structure as a mask to form an annular semiconductor fin;
• epitaxially growing a first bottom source/drain structure within the annular semiconductor fin and a second bottom source/drain structure surrounding the annular semiconductor fin;
• forming a first silicide layer over the first bottom source/drain structure and a second silicide layer over the second bottom source/drain structure;
• forming a first gate structure over the first silicide layer and a second gate structure over the second silicide layer;
• epitaxially growing a top source/drain structure over the annular semiconductor fin;
• and
• forming a contact structure over the top source/drain structure, comprising:
• forming a lower contact of the contact structure over the top source/drain structure;
• forming a middle contact of the contact structure over the lower contact;
• and
• forming an upper contact over the middle contact,
• wherein a width of the upper contact is greater than a width of the middle contact.