Semiconductor devices and methods of forming the same are provided. In one embodiment, a semiconductor device includes a contact feature in a first dielectric layer, a first passivation layer over the contact feature, a bottom conductor plate layer disposed over the first passivation layer and including a first plurality of sublayers, a second dielectric layer over the bottom conductor plate layer, a middle conductor plate layer disposed over the second dielectric layer and including a second plurality of sublayers, a third dielectric layer over the middle conductor plate layer, a top conductor plate layer disposed over the third dielectric layer and including a third plurality of sublayers, and a second passivation layer over the top conductor plate layer.