Semiconductor device structures comprising a gate structure having different profiles at different portions of the gate structure are provided. In some examples, a semiconductor device includes a fin structure on a substrate, a source/drain structure on the fin structure, and a gate structure over the fin structure and along a sidewall of the fin. The source/drain structure is proximate the gate structure. The gate structure has a top portion having a first sidewall profile and a bottom portion having a second sidewall profile different from the first sidewall profile.