Method of forming semiconductor device

Abstract

The invention discloses a formation method of a semiconductor device. The method comprises the following steps: providing a semiconductor substrate including a storage area and a logic area; forming a plurality of first polysilicon layers at the storage area; forming a control gate medium material layer covering the first polysilicon layers; forming a second polysilicon layer covering the control gate medium material layer and the logic area; etching a part of the second polysilicon layer and the control gate medium material layer to form a second openings exposing a part of the surfaces of the top portions of the first polysilicon layers; forming a third polysilicon layer covering the second polysilicon layer; etching a part of the third polysilicon layer, the second polysilicon layer, the control gate medium material layer and the first polysilicon layers at the storage area to form a selection grid of a flash memory device, a floating gate and a control grid disposed on the floating gate; forming a protective layer covering the selection grid and the control grid; forming a photoresist layer on the protective layer; and etching the third polysilicon layer and the second polysilicon layer at the logic area to form a grid of a logic transistor. According to the invention, recesses on the control grid and the selection grid are prevented.

Description

technical field [0001] The invention relates to the field of semiconductor manufacturing, in particular to a method for forming a semiconductor device. Background technique [0002] In the current semiconductor industry, integrated circuit products can be mainly divided into three types: logic, memory and analog circuits, among which memory devices account for a considerable proportion of integrated circuit products. Among memory devices, flash memory devices (flash memory) have developed particularly rapidly in recent years. Its main feature is that it can keep stored information for a long time without power on, and has many advantages such as high integration, fast access speed, easy erasure and rewriting, etc. The field has been widely used. [0003] A schematic structural view of an existing flash memory device, including: a semiconductor substrate, a separate storage transistor gate stack and a selection transistor gate stack located on the semiconductor substrate, a...

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Problems solved by technology

[0004] In the prior art, when making a flash memory device, it is usually necessary to integrate logic transistors in other regions of the semiconductor substrate. The gate of the logic transistor uses the same layer of polysilicon as the control gate and selection gate of the flash memory device, and the flash memory device and the logic transistor are integrated. In the integrated manufacturing process, the flash memory device is generally fabricated first, and then the logic transistor is fabricated. When forming the gate of the logic transistor, it is easy to over-etch the surface of the control gate and selection gate of the flash memory device that has been formed. recessed defect

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