A semiconductor structure includes a SiGe fin protruding from a substrate, where the SiGe fin includes a top portion having a first sidewall and a second sidewall and a bottom portion having a third sidewall and a fourth sidewall, and where a first transition region connecting the first sidewall to the third sidewall and a second transition region connecting the second sidewall to the fourth sidewall each have a tapered profile extending away from the first sidewall and the second sidewall, respectively, and a Si-containing layer disposed on the top portion of the SiGe fin, where a portion of the Si-containing layer on the first transition region extends away from the first sidewall by a first lateral distance and a portion of the Si-containing layer on the second transition region extends away from the second sidewall by a second lateral distance that is different from the first lateral distance.