Method of manufacturing semiconductor device

Abstract

A memory transistor and a high breakdown voltage MOS transistor are easily formed on the same semiconductor substrate without changing the operational characteristics of the memory transistor. The process of forming the tunnel insulation film of the memory transistor and the process of forming the gate insulation film of the MOS transistor are performed separately. Concretely, an insulation film to be a part of the tunnel insulation film and a silicon nitride film are formed on the whole surface, and then the silicon nitride film in a MOS transistor formation region is selectively removed using a photoresist layer. Then, the MOS transistor formation region is selectively oxidized using the remaining silicon nitride film as an anti-oxidation mask to form the gate insulation film of the MOS transistor having a selected thickness.

Description

technical field [0001] The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device including a split-gate nonvolatile memory transistor and a MOS transistor. Background technique [0002] In recent years, an electrically erasable and program-readable dedicated storage device (hereinafter referred to as EEPROM) has been widely used as a flash memory due to the expansion of application fields such as mobile phones and digital cameras. [0003] EEPROM stores multi-valued digital data of two or more values ​​by whether a specified amount of charge is stored in the floating gate (floating gate), and by detecting the conduction change of the channel region corresponding to the amount of charge, Digital data can be read. [0004] The EEPROM is classified into: a stacked-gate type (Stacked-Gate Type) having a structure in which a floating gate and a control gate are sequentially stacked...

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Problems solved by technology

Therefore, considering the operation characteristics (threshold voltage, storage current value, etc.)

In the conventional manufacturing method, as described above, since the manufacturing process of the tunnel insulating film and the gate insulating film of the MOS transistor are the same, it is ideal in that the manufacturing process can be simplified. However, in order to make the MOS transistor high Withstanding voltage, when the film thickness of the gate insulating film is increased, the thickness of the tunnel insulating film of the memory transistor becomes too thick at the same time, and the operating characteristics of the memory element deteriorate

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