An integrated circuit includes an upper semiconductor body extending in a first direction from an upper source region to an upper drain region, and a lower semiconductor body extending in the first direction from a lower source region to a lower drain region. The upper body is spaced vertically from the lower body in a second direction orthogonal to the first direction. A gate spacer structure is adjacent to the upper and lower source regions. In an example, the gate spacer structure includes (i) a first section having a first dimension in the first direction, and (ii) a second section having a second dimension in the first direction. In an example, the first dimension is different from the second dimension by at least 1 nm. In some cases, an intermediate portion of the gate spacer structure extends laterally within a given gate structure, or between upper and lower gate structures.