A first gate-all-around (GAA) transistor and a second GAA transistor may be formed on a substrate. The first GAA transistor includes at least one silicon plate, a first gate structure, a first source region, and a first drain region. The second GAA transistor includes at least one silicon-germanium plate, a second gate structure, a second source region, and a second drain region. The first GAA transistor may be an n-type field effect transistor, and the second GAA transistor may be a p-type field effect transistor. The gate electrodes of the first gate structure and the second gate structure may include a same conductive material. Each silicon plate and each silicon-germanium plate may be single crystalline and may have a same crystallographic orientation for each Miller index.