The present disclosure describes a semiconductor device and methods for forming the same. The semiconductor device includes nanostructures on a substrate and a source/drain region in contact with the nanostructures. The semiconductor device also includes a gate structure that includes first and second portions. The first portion is formed between each nanostructure of nanostructures. The second portion is formed under the bottom-most nanostructure of the plurality of nanostructures and extends under a top surface of the substrate.