A variable frequency solid-state oscillator having on a surface of a trapezoid-shaped semiconductor substrate a laterally trapezoid-shaped epitaxial layer of N-type semiconductor monocrystal, the four sides of the trapezoid being planes of cleavage, a negative electrode being provided on the shorter side of the parallel opposite sides of the semiconductor layer on the substrate, and a positive electrode being provided on the longer side of the parallel opposite sides of the semiconductor layer on the substrate. Said oscillator oscillates with a frequency corresponding to the applied voltage when various values of voltage are applied to said device through said electrodes with means for applying excitation voltages.