Semiconductor memory device using hot electron injection
AssigneeOki Semiconductor Co., Ltd.
InventorKatsutoshi Saeki
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Abstract
A semiconductor memory device has a low-resistivity semiconductor substrate on which a higher-resistivity semiconductor layer of the same conductivity type is formed. Memory cell transistors are formed in the semiconductor layer. A diffusion region, also of the same conductivity type, is formed below the memory cell transistors. The resistivity of the diffusion region is lower than the resistivity of the semiconductor layer. In the programming of data into the memory cell transistors by hot electron injection, the diffusion region reduces the voltage drop due to current flow from the part of the semiconductor layer near the memory cell transistors into the semiconductor substrate, thereby reducing unwanted elevation of the potential of the semiconductor layer.
Claims14
A semiconductor memory device in which data are programmed by hot electron injection, the semiconductor memory device comprising:
- a semiconductor substrate of a first conductivity type, having a first resistivity;
- a semiconductor layer disposed on the semiconductor substrate, the semiconductor layer being of the first conductivity type and having a second resistivity higher than the first resistivity;
- a memory cell transistor formed in the semiconductor layer, the memory cell transistor including a source region, a drain region, a gate insulating layer, and a gate electrode, the gate insulating layer and the gate electrode being disposed between the source region and the drain region, the gate insulating layer insulating the gate electrode from the semiconductor layer;
- and
- a diffusion region disposed in the semiconductor layer below the memory cell transistor, the diffusion region being contiguous with the semiconductor substrate and spaced apart from the memory cell transistor, the diffusion region having a third resistivity lower than the second resistivity.
Dependencies are inferred from the claim text.