A semiconductor device that is a surface mount-type device includes a nitride semiconductor chip including a silicon substrate having a first thermal expansion coefficient and an InxGayAl1-x-yN layer in contact with a surface of the silicon substrate, where 0≤x≤1, 0≤y≤1, 0≤x+y≤1; and a die pad including Cu and having a second thermal expansion coefficient that is greater than the first thermal expansion coefficient. A thickness of the nitride semiconductor chip is at least 0.2 mm, length L of the nitride semiconductor chip is at least 3.12 mm, and thickness tm of the die pad and length L of the nitride semiconductor chip satisfy tm≥2.00×10−3×L2+0.173, tm being a thickness in mm and L being a length in mm.