The invention provides a semiconductor device, having a variety of functions such as a bistable memory and a logic circuit, in which a MOS semiconductor element, a resonance tunnel diode, a hot electron transistor and the like are formed on a common substrate. An n-type Si layer and a p-type Si layer surrounded with an isolation oxide film are formed on an SOI substrate. A mask oxide film and a gate oxide film are formed, and the n-type Si layer is subjected to crystal anisotropic etching by using the mask oxide film as a mask, so as to change the n-type Si layer into the shape of a thin Si plate. After first and second tunnel oxide films are formed on side faces of this n-type Si layer, first and second polysilicon electrodes of a resonance tunnel diode and a polysilicon electrode working as a gate electrode of a MOS semiconductor element are formed out of a common polysilicon film. Thus, a Si/SiO.sub.2 type quantum device can be manufactured with ease at a low cost.