SEMICONDUCTOR DEVICE

PURPOSE:To determine a breakdown strength by the thickness of a depletion layer only and improve a reproducibility by building up a nondoped GaAs layer and a GaAs layer which are in a lattice-matching state on an AlGaAs layer. CONSTITUTION:A nondoped GaAs layer 2, a nondoped AlxGa1-xAs (x=0.22) layer 3, an n-type AlxGa1-xAs layer 4, a nondoped GaAs layer 5 and an n-type GaAs layer 6 which are in a lattice-matching state are built up on a substrate 1 in this order by epitaxial growth. A depletion layer which is formed in the n-type GaAs layer 6 surface spread in accordance with the extent of the side etching of a recess 8 is defined by the area of the surface. On the other hand, a depletion layer formed in the nondoped GaAs layer 5 is defined by the thickness of the layer 5 and a breakdown strength can be determined by the film thickness.