Semi-floating gate memory device with u-shaped trench and preparation method thereof

Abstract

A semi-floating gate storage device with a U-shaped trench and its preparation method, the device comprising: a semiconductor substrate with a first-type doping, and a source region and a drain region with a second-type doping on the semiconductor substrate There is a U-shaped groove in the semiconductor substrate, the U-shaped groove is located between the source region and the drain region, and the sidewall and bottom surface of the U-shaped groove are covered with a first layer of dielectric film; formed on the first layer of dielectric film There is a contact window, and a half-floating gate with the first type of doping is formed on the first layer of dielectric film and in the U-shaped trench. The half-floating gate is in contact with the drain region through the window of the first layer of dielectric film, and the ultra-shallow junction is used. Form a p-n junction diode; cover the top of the half-floating gate to form a second layer of dielectric film; form a control gate on the second layer of dielectric film; Doped source and drain heavily doped regions. Therefore, the present invention can improve the access speed and ensure that the performance parameters between devices are relatively consistent under low operating voltage.

Description

technical field [0001] The present invention relates to the field of integrated circuit manufacturing, in particular to the technical field of semiconductor storage devices, in particular to a semi-floating gate storage device with a U-shaped trench using a gate-last process and a preparation method. Background technique [0002] As semiconductor memory is widely used in various electronic products, different application fields have different requirements on the structure, performance and density of semiconductor memory. For example, Static Random Access Memory (SRAM) has high random access speed and low integration density, while standard Dynamic Random Access Memory (DRAM) has high density and Moderate random access speed. [0003] Commonly used flash memory chips such as USB flash drives use a device called a floating gate transistor. Flash memory is also called "non-volatile memory". The so-called "non-volatile" means that when the chip is not powered, the information...

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Problems solved by technology

[0007] Moreover, the PN junction of the semi-floating gate storage device in the above-mentioned patent documents is formed earlier in the entire front-end process, and undergoes multi-step annealing, and the junction depth fluctuates greatly, which further leads to the following problems:

[0008] ①. The threshold voltage of the side vertical channel MOSFET fluctuates greatly;

[0009] ②. The performance of the semi-floating gate storage devices produced by the above-mentioned patent documents varies greatly among individuals, making it impossible to carry out large-scale integration

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