SILICON CARBIDE SEMICONDUCTOR DEVICE AND SILICON CARBIDE SEMICONDUCTOR SUBSTRATE

First and second buffer regions and an n−-type drift region are sequentially formed by epitaxial growth on an n+-type starting substrate. An impurity concentration of the first buffer region is higher than that of the n−-type drift region and lower than that of the n+-type starting substrate. An impurity concentration of the second buffer region is higher than that of the first buffer region and continuously increases by a first impurity concentration gradient from a first gradient changing point toward the n−-type drift region to a second gradient changing point toward the first buffer region; continuously decreases by a second impurity concentration gradient from the first gradient changing point to a first interface; and continuously decreases by a third impurity concentration gradient from the second gradient changing point to a second interface. The second impurity concentration gradient is lower than the third impurity concentration gradient.