A semiconductor device includes: a base including a base surface; a mesa protruding from the base surface in a first direction intersecting the base surface, the mesa including a top surface and two side surfaces on both sides of the top surface, and extending along the base surface; and an electric resistor including a top wall provided on the top surface and a side wall provided on at least one of the two side surfaces, the electric resistor being configured such that a current flows in an extending direction of the mesa.