SEMICONDUCTOR DEVICE

摘要

PROBLEM TO BE SOLVED: To suppress leakage current in a substrate-gate direction in a semiconductor device such as a field effect transistor using a nitride semiconductor.SOLUTION: A semiconductor device comprises: a buffer layer formed on a substrate; a strained superlattice buffer layer formed on the buffer layer; an electron transit layer which is formed on the strained superlattice buffer layer and formed by a semiconductor material; and an electron supply layer which is formed on the electron transit layer and formed by a semiconductor material. The buffer layer is formed by AlGaN and includes two and more layers having different Al composition ratios. The strained superlattice buffer layer is formed by alternately laminating AlN-containing first lattice layers and GaN-containing second lattice layers. A layer which contacts the strained superlattice buffer layer among the two and more layers having different Al composition ratios in the buffer layer is formed to have an Al composition ratio equal to or more than an effective Al composition ratio in the strained superlattice buffer layer.