Semiconductor devices that each include a channel region and a gate stack are disclosed. The gate stack includes a gate insulator, a pair of spaced apart first metal gate layers, and a second metal gate layer. The gate insulator extends along the length of the channel region. The first metal gate layers have a first workfunction and extend from the gate insulator. The second metal gate layer is disposed between the first metal gate layers, has a second workfunction different from the first workfunction, and extends from the gate insulator. Methods of fabricating the gate stack are also disclosed.