Thin channel region on wide subfin

A method comprising:

• forming a trench within an insulation layer and on a substrate;
• forming a fin, which includes InP, within the trench with a portion of the fin extending over the trench;
• polishing the portion of the fin that extends over the trench to a level generally coplanar with a top surface of the insulation layer;
• removing an upper portion of the fin, located within the trench, to provide a recess within the trench extending downwards to an upper surface of the fin remainder;
• forming a III-V material within the recess and directly on the upper surface of the fin remainder to form a fin structure including a fin lower portion, which includes the fin remainder, and a fin upper portion, which includes the III-V material;
• removing a portion of the insulation layer adjacent side walls of the fin upper portion;
• and
• removing lateral portions of the fin upper portion so the fin upper portion has a bottom surface with a bottom maximum width and the fin lower portion has an upper surface with an upper maximum width that is greater the bottom maximum width.

A device comprising:

• a fin structure including upper and lower portions, the upper portion having a bottom surface directly contacting an upper surface of the lower portion;
• wherein (a) the lower portion is included in a trench;
• (b) the bottom surface has a bottom maximum width wider than an upper maximum width of the upper surface;
• (c) the bottom surface covers a middle portion of the upper surface but not lateral portions of the upper surface;
• and (d) the upper portion includes an upper III-V material and the lower portion includes a lower III-V material different from the upper III-V material.