A semiconductor device according to embodiments described herein includes a p-type SiC layer, a gate electrode, and a gate insulating layer between the SiC layer and the gate electrode. The gate insulating layer includes a first layer, a second layer, a first region, and a second region. The second layer is between the first layer and the gate electrode and has a higher oxygen density than the first layer. The first region is provided across the first layer and the second layer, includes a first element from F, D, and H, and has a first concentration peak of the first element. The second region is provided in the first layer, includes a second element from Ge, B, Al, Ga, In, Be, Mg, Ca, Sr, Ba, Sc, Y, La, and lanthanoid, and has a second concentration peak of the second element and a third concentration peak of C.