Semiconductor device structures and methods for manufacturing the same are provided. The semiconductor device structure includes a substrate, a first nitride semiconductor layer, a second nitride semiconductor layer, a first dielectric layer and a second dielectric layer. The first nitride semiconductor layer is disposed on the substrate. The second nitride semiconductor layer is disposed on the first nitride semiconductor layer and has a bandgap greater than that of the first nitride semiconductor layer. The first dielectric layer is disposed on the second nitride semiconductor layer. The second dielectric layer is disposed on the first dielectric layer. The second dielectric layer includes a first portion and a second portion separated from the first portion by a trench, wherein the trench terminates at an upper surface of the first dielectric layer.