Abstract
Semiconductor device structures and methods for manufacturing the same are provided. The semiconductor device structure includes a substrate, asemiconductor layer on the substrate, and a patterned dielectric layer disposed on the substrate and covered by the semiconductor layer. The patterned dielectric layer is configured to prevent a constituent in the semiconductor layer from diffusing into the substrate. The semiconductor device structure further includes a first nitride semiconductor layer on the semiconductor layer and a second nitride semiconductor layer on the first nitride semiconductor layer. A band gap of the second nitride semiconductor layer is greater than a band gap of the first nitride semiconductor layer.