The conductance dependences of the edge channels of silicon nanosandwich structures (SNS) on the vertical gate voltage V_g are studied. The experiments are carried out in such a range of V_g, in which the two-dimensional density of holes p_2D is stable that made it possible to avoid the changes of the Fermi level position and thereby to unambiguously identify the Aharonov–Casher oscillations. The effect of a spin field-effect transistor at a high temperature (T = 77 K) is demonstrated, which manifests itself in the form of Aharonov–Casher oscillations of longitudinal conductance depending on V_g, which controls the Bychkov–Rashba spin-orbit interaction. This experiment became possible due to the high degree of spin polarization of holes and the long spin-lattice relaxation time because of the extremely small width of the silicon quantum well and the narrowness of its edge channels, which is ensured by the properties of the negative-U-barriers limiting them effectively decreasing the electron-electron interaction.