A semiconductor device with doped shallow trench isolation (STI) structures and a method of fabricating the same are disclosed. The method includes forming a fin structure on a substrate, forming a superlattice structure with first and second nanostructured layers arranged in an alternating configuration on the fin structure, depositing an oxide liner surrounding the superlattice structure and the fin structure in a first deposition process, forming a dopant source liner on the oxide liner, depositing an oxide fill layer on the dopant source liner in a second deposition process different from the first deposition process, performing a doping process to form a doped oxide liner and a doped oxide fill layer, removing portions of the doped oxide liner, the doped oxide fill layer, and the dopant source liner from sidewalls of the superlattice structure, and forming a gate structure on the fin structure and surrounding the first nanostructured layers.

A SiC semiconductor device manufacturing method includes a step of etching a surface of a SiC substrate 1 with H.sub.2 gas under Si-excess atmosphere within a temperature range of 1000 C. to 1350 C., a step of depositing, by a CVD method, a SiO.sub.2 film 2 on the SiC substrate 1 at such a temperature that the SiC substrate 1 is not oxidized, and a step of thermally treating the SiC substrate 1, on which the SiO.sub.2 film 2 is deposited, in NO gas atmosphere within a temperature range of 1150 C. to 1350 C.

A semiconductor device structure and a formation method are provided. The method includes forming a sacrificial base layer over a substrate and forming a semiconductor stack over the sacrificial base layer. The semiconductor stack has multiple sacrificial layers and multiple semiconductor layers laid out alternately. The method also includes forming a gate stack to partially cover the sacrificial base layer, the semiconductor layers, and the sacrificial layers. The method further includes removing the sacrificial base layer to form a recess between the substrate and the semiconductor stack. In addition, the method includes forming a metal-containing dielectric structure to partially or completely fill the recess. The metal-containing dielectric structure has multiple sub-layers.