FinFET with curved STI

A semiconductor structure, comprising:

• a substrate having a fin structure thereon;
• a first isolation oxide structure having a first curved top surface disposed on one side of the fin structure, wherein the first isolation oxide structure has a first uppermost edge that is in contiguous with a first sidewall of the fin structure, wherein a first angle is defined between a tangent to the first uppermost edge that contacts the first sidewall and the first sidewall, wherein the first angle is approximately 130-140 degrees;
• a second isolation oxide structure having a second curved top surface disposed on the other side of the fin structure opposite to the first isolation oxide structure, wherein the first isolation oxide structure and the second isolation oxide structure have different depths, wherein the second isolation oxide structure has a second uppermost edge that is in contiguous with a second sidewall of the fin structure, wherein a second angle is defined between a tangent to the second uppermost edge that contacts the second sidewall and the second side wall, and wherein the second angle is approximately 125-135 degrees;
• a gate disposed on the fin structure;
• a gate dielectric layer disposed between the plurality of fin structure and the gate;
• and
• a source/drain doped region in the fin structure.