Semiconductor device and method of fabricating semiconductor device

A semiconductor device comprises an Si substrate (1), a stress absorbing layer (2) comprising GaAs and disposed on the Si substrate (1), a compound buffer layer (3) having a composition of AlxGa1-x-yInyN (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) and disposed on the stress absorbing layer (2), and a compound semiconductor layer (4) having a composition of AlxGa1-x-yInyN (0 ≤ x ≤ 1, 0 ≤ y ≤ 1) and disposed on the buffer layer (3). Therefore, the buffer layer (3) protects the GaAs stress absorbing layer (2) from high temperatures during the formation of the compound semiconductor layer (4), whereby the stress absorbing layer (2) is prevented from decomposition. As a result, a stress due to lattice mismatch or thermal stress between the Si substrate (1) and the compound semiconductor layer (4) is absorbed in the GaAs stress absorbing layer (2) having a lowest bulk modulus, whereby the compound semiconductor layer (4) with reduced dislocations is grown on the buffer layer (3) and bending of the Si substrate (1) is prevented.