Semiconductor structure having isolations between fins and comprising materials with different thermal expansion coefficients (CTE)

A semiconductor structure, comprising:

• a substrate having fin structures, the substrate comprising a material having a substrate thermal expansion coefficient;
• a first isolation structure and a second isolation structure between the fin structures, the first isolation structure having a first depth measured from a topmost surface to a bottommost surface of the first isolation structure, and the second isolation structure having a second depth measured from a topmost surface to a bottommost surface of the second isolation structure, wherein the first depth is greater than the second depth;
• and
• a liner sandwiched between the first and second isolation structures and the substrate and between the first and second isolation structures and the fin structures, wherein the liner comprises a high-k dielectric material,
• wherein the first isolation structure comprises a first dielectric material having a first thermal expansion coefficient and a second dielectric material having a second thermal expansion coefficient, the first thermal expansion coefficient of the first dielectric material is less than a thermal expansion coefficient of the high-k dielectric material of the liner, and the first thermal expansion coefficient of the first dielectric material is greater than the second thermal expansion coefficient of the second dielectric material,
• wherein the second isolation structure comprises the first dielectric material and the second dielectric material,
• wherein the substrate thermal expansion coefficient is in between the first thermal expansion coefficient and the second thermal expansion coefficient,
• wherein the first isolation structure has a first tapered surface coupling a bottom surface and a sidewall of the first isolation structure, the second isolation structure has a second tapered surface coupling a bottom surface and a sidewall of the second isolation structure,
• wherein sidewalls and a bottom of the second dielectric material of the first isolation structure are separated from the liner by the first dielectric material of the first isolation structure, and sidewalls and a bottom of the second dielectric material of the second isolation structure are separated from the liner by the first dielectric material of the second isolation structure, and
• wherein the fin structures are exposed from the liner.

A semiconductor structure, comprising:

• a substrate having fin structures, the substrate comprising a material having a substrate thermal expansion coefficient;
• a first isolation structure and a second isolation structure between the fin structures, the first isolation structure having a first width and the second isolation structure having a second width, wherein the first width is greater than the second width, the first isolation structure has a first tapered surface coupling a bottom surface and a sidewall of the first isolation structure, the second isolation structure has a second tapered surface coupling a bottom surface and a sidewall of the second isolation structure;
• and
• a first dielectric liner sandwiched between the first isolation structure and the substrate, and a second dielectric liner sandwiched between and second isolation structure and the substrate, wherein the first dielectric liner and the second dielectric liner comprise a high-k dielectric material,
• wherein the first isolation structure comprises a first dielectric material having a first thermal expansion coefficient and a second dielectric material having a second thermal expansion coefficient, the first thermal expansion coefficient of the first dielectric material is less than a thermal expansion coefficient of the high-k dielectric material of the first and second dielectric liners, and the first thermal expansion coefficient of the first dielectric material is greater than the second thermal expansion coefficient of the second dielectric material,
• wherein the second isolation structure comprises the first dielectric material and the second dielectric material, the first dielectric material is sandwiched between the second dielectric material and the substrate,
• wherein the substrate thermal expansion coefficient is in between the first thermal expansion coefficient and the second thermal expansion coefficient,
• wherein sidewalls and a bottom of the second dielectric material of the first isolation structure are separated from the first dielectric liner by the first dielectric material of the first isolation structure, and sidewalls and a bottom of the second dielectric material of the second isolation structure are separated from the second dielectric liner by the first dielectric material of the second isolation structure,
• wherein the fin structures are exposed from the first dielectric liner and the second dielectric liner, and
• wherein a bottommost surface of the first dielectric liner and a bottommost surface of the second dielectric liner are at different levels.