Similar to FinFET device 200, FinFET device 400 includes substrate 210 and fin structure 220, which includes fins 222 extending from substrate 210. In FIG. 4, fins 222 extend from substrate 210 in a z-direction, such that fins 222 have heights defined in the z-direction (such as height h), lengths defined in an x-direction, and widths and/or spacings defined in a y-direction (such as width w₁, width w₂, width w₃, spacing S₁, spacing S₂, and spacing S₃). Each fin 222 has a channel region 402, a source region 404, and a drain region 406 defined along the length of respective fins 222 (here, along the x-direction), where channel region 402 is disposed between source region 404 and drain region 406 (generally referred to as source/drain regions). Each channel region 402 includes a top portion defined between sidewall portions of a respective fin 222, where the top portion and the sidewall portions engage with a gate structure 410 (described in detail below), such that current can flow between a respective source region 404 and a respective drain region 406 during operation of FinFET device 400. In FIG. 4, gate structure 410 blocks view of channel regions 402 of fins 222. In some implementations, the top portion is a substantially horizontal side (for example, substantially parallel to an x-y plane) of fins 222, while the two sidewall portions are substantially vertical sides (for example, substantially parallel to an x-z plane) of fins 222.