Fin structure with reduced defects and manufacturing method thereof

A method, comprising:

• implanting a first dopant and carbon in a first portion of a substrate of a semiconductor device;
• implanting a second dopant and carbon in a second portion of the substrate;
• depositing a first silicon-based layer on the first portion of the substrate and the second portion of the substrate;
• etching a recessed portion extending through the first silicon-based layer,
• wherein the recessed portion extends into the first portion of the substrate;
• depositing a seed layer in the recessed portion,
• wherein the seed layer lines side surfaces and a bottom surface of the recessed portion;
• depositing a second silicon-based layer within the recessed portion,
• wherein the second silicon-based layer is deposited on the seed layer;
• etching the second silicon-based layer, the seed layer, the first portion of the substrate, the first silicon-based layer, and the second portion of the substrate to form a plurality of fin structures;
• and
• forming a set of isolation structures disposed between fin structures of the plurality of fin structures,
• wherein each fin structure of a first subset of the plurality of fin structures includes a first diffusion region between part of the first portion of the substrate and part of the seed layer,
• wherein the first diffusion region includes carbon diffused into silicon and has a top surface at a first height above the substrate,
• wherein each fin structure of a second subset of the plurality of fin structures includes a second diffusion region between part of the second portion of the substrate and part of the first silicon-based layer,
• wherein the second diffusion region includes carbon diffused into silicon and has a top surface at a second height above the substrate,
• wherein the first height is less than or equal to a third height of an isolation structure of the set of isolation structures and the second height is greater than or equal to the third height,
• wherein a bottom surface of the second diffusion region is at a fourth height above the substrate, and
• wherein the fourth height is greater than or equal to the third height.

A method, comprising:

• forming a first set of fin structures on a substrate of a semiconductor device, a first fin structure of the first set of fin structures comprising:
• a first fin portion including an n-type dopant and carbon co-implanted in a first silicon-based material
• a second fin portion, disposed above the first fin portion, including a first carbon-free silicon-based material, and
• a third fin portion, disposed between the first fin portion and the second fin portion, including a diffusion region that includes carbon diffused into silicon,
• wherein a top surface of the third fin portion is at a first height above the substrate, and
• wherein the first height is less than or equal to a second height of a trench structure disposed between fin structures of the first set of fin structures;
• and
• forming a second set of fin structures on the substrate, a second fin structure of the second set of fin structures comprising:
• a fourth fin portion including a p-type dopant and carbon co-implanted in a second silicon-based material,
• a fifth fin portion, disposed above the fourth fin portion, including a second carbon-free silicon-based material, and
• a sixth fin portion, disposed between the fourth fin portion and the fifth fin portion, including a diffusion region that includes carbon diffused into silicon,
• wherein a bottom surface of the sixth fin portion is at a third height above the substrate, and
• wherein the third height is greater than or equal to a fourth height of a trench structure disposed between fin structures of the second set of fin structures.