Non-volatile memory has wide applications in technology fields such as mobile communications, data terminals, multi-media, consumer electronics, defense electronic equipment, and so on. The rapid increase in data storage capacity places higher demand on high density, high speed, low energy consumption and long endurance memories.
Polysilicon floating-gate non-volatile semiconductor memory constitutes mainstream non-volatile semiconductor memory technology, occupying a major portion of the non-volatile semiconductor memory market, and becoming the fastest developing non-volatile semiconductor memory. Chips having polysilicon non-volatile semiconductor memory devices are shrinking proportionally, following basically Moore's law, i.e., the degree of integration of semiconductor chips increases by doubling every 18 months. Generally speaking, programming and erasure of a polysilicon floating-gate non-volatile semiconductor memory device are done by hot channel electron injection and Fowler-Nordheim tunneling. The programming of the polysilicon floating-gate non-volatile semiconductor memory device is done by hot-channel electron injection near a drain terminal, while the erasure is realized by tunneling through a channel oxidization layer. Generally, the source and drain terminals of polysilicon floating-gate non-volatile semiconductor memory devices are both P-N junctions.
As the device sizes shrink further, however, the channel length of the above mentioned polysilicon floating-gate non-volatile semiconductor memory devices becomes shorter and shorter, and the challenges faced by related technologies become greater and greater. The main challenge relates to the difficulty to reduce programming voltage while still generating sufficient amount of hot electron injections at the drain terminal. The P-N junction structures at both source and drain result in low hot electron injection efficiency, slow programming speed, and high energy consumption. A newly proposed device structure uses Schottky junction structures at both source and drain, but a polysilicon floating-gate non-volatile semiconductor memory device having Schottky junction structures at both source and drain tend to have relatively large leakage current, resulting in low reliability of the polysilicon floating-gate non-volatile semiconductor memory device.
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