Abstract: A power transistor device is provided which has a function of clamping the collector voltage to a stable level for a wide range of temperature variations. In the power transistor device, a plurality of pn junctions are formed to fabricate Zener diodes in the polycrystalline silicon film in the form of rings. The ring configuration of the Zener diodes eliminates an end at the pn junction and prevents the junction surface from being exposed, making it possible to use as a stable Zener voltage the dielectric strength characteristic of the pn junction having a very small temperature coefficient.

Abstract: A vertical semiconductor memory device is provided which capable of miniaturization. More particularly, a memory cell is provided having a trench capacitor and a vertical transistor in a dynamic random access memory suitable for high density integration. An object of this arrangement is to provide a vertical memory cell capable of miniaturization for use in a ultra-high density integration DRAM of a Gbit class. This memory cell is characterized in that each memory cell is covered with an oxide film, an impurity area does not exist on the substrate side, an area in which a channel area is formed is a hollow cylindrical single crystal area, connection of impurity areas as source-drain areas and bit lines and the electrode of a capacitor is made by self-alignment and connection between a word line electrode and a gate electrode is also made by self-alignment.