Memory, flash memory unit capable of being programmed for multiple times and preparation method of flash memory unit

Abstract

The invention provides a memory, a multi-time programmable flash memory unit and a preparation method thereof, the flash memory unit adopts a single-layer polysilicon gate structure and comprises a P-type selection tube, a P-type storage transistor and a transistor capacitor, the gate of the P-type storage transistor is floated to store charges, the extension part of the P-type storage transistor serves as a pole plate of the transistor capacitor, and the P-type selection tube is connected with the transistor capacitor. The substrate of the P-type storage transistor and the substrate of the transistor capacitor C1 are isolated through a shallow trench. According to the P-type storage transistor, the programming operation of the storage unit is executed through hot carrier injection, and the erasing operation is executed through the F-N tunneling effect of the substrate and the floating gate. According to the invention, only one trap (NW) injection is adopted, and then the P-type injection with lower concentration is added at the control gate to improve the junction breakdown voltage between the control gate and the N trap, so that the existing technological process is simplified, the distance between different traps is removed, the area of the flash memory unit is reduced, and the cost is reduced.

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