Semiconductor memory device and preparation method thereof

Abstract

The invention relates to a semiconductor memory device and a preparation method thereof. The method comprises the following steps: providing a semiconductor substrate and forming a tunneling oxide layer, a floating gate layer and a mask layer on the semiconductor substrate; patterning the mask layer, the floating gate layer, the tunneling oxide layer and the semiconductor substrate to form shallow trenches in the semiconductor substrate on the two sides of a floating gate laminate while the floating gate laminate is formed; selecting an isolation material to fill the shallow trenches so as to form a shallow trench isolation structure; removing the mask layer to form a groove on the upper side of the floating gate layer; etching back the isolation material on the two sides of the groove to increase the critical size of the groove; depositing a semi-spherical floating gate film at the bottom and on the side wall of the groove with the increased critical size to form a floating gate structure. The floating gate structure comprises a semi-spherical floating gate film, so the surface area of the floating gate structure is increased, the electric capacity formed by the floating gate is increased, and the performance of the device is improved.

Description

technical field [0001] The present invention relates to a semiconductor memory device, in particular, the present invention relates to a semiconductor memory device and a manufacturing method thereof. Background technique [0002] With the rapid development of portable electronic devices (such as mobile phones, digital cameras, MP3 players, and PDAs, etc.), the requirements for data storage are getting higher and higher. Non-volatile memory has become the most important storage component in these devices because of its ability to save data even when power is off. Among them, because flash memory (flash memory) can achieve a high chip storage density, and no new materials are introduced , The manufacturing process is compatible, therefore, it can be more easily and reliably integrated into own digital and analog circuits. [0003] Floating gate structure memory is one of the important flash memory devices, and it is a mainstream memory type that is widely used and generally ...

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Problems solved by technology

[0005] The floating gate structure prepared in the prior art has a relatively large coupling ratio, among which such as Figure 1d As shown, the tunnel capacitance Ctunnel=Cgs+Cgb+Cgd, the total capacitance of the device Ctotal=Cono+Ctunnel, where Kono=Cono/Ctotal, because the device has a low coupling rat

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