Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – Having insulated gate
Reexamination Certificate
1999-02-03
2001-01-30
Booth, Richard (Department: 2812)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
Having insulated gate
C438S527000
Reexamination Certificate
active
06180455
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a semiconductor device having a semiconductor substrate with a double well structure in which two wells different in conductivity from each other are formed within the semiconductor substrate and a method of manufacturing the semiconductor device.
2. Description of the Related Art
The following semiconductor substrate may be used to manufacture a semiconductor memory device including a nonvolatile semiconductor element such as an EP-ROM (Erasable and Electrically Programmable Read Only Memory) or an EEP-ROM (Electrically-Erasable Programmable Read Only Memory), or a CMOS (Complementary Metal-Oxide Semiconductor). This type of semiconductor substrate has a first well portion and a second well portion. The first well portion is exposed onto the surface of the semiconductor substrate and different in conductivity from the substrate. The second well portion is formed so as to be bared on the surface of the semiconductor substrate in the first well portion and is identical in conductivity to the substrate.
The semiconductor substrate having such a double well structure includes the following forming process. The first well portion is formed by injecting impurity ions into the semiconductor substrate. Further, ions (hereinafter called “channel stop ions”) for forming channel stop regions are injected into a field insulating film forming region excluding the first well portion of the substrate. After the formation of field insulating films, the second well portion is formed within the first well portion by the injection of the impurity ions.
The second well portion has a plurality of active regions. These active regions are used as a memory array region portion for a non-volatile storage element and a peripheral element region portion for circuits around the non-volatile storage element.
The impurity ions, which have been injected to form the second well portion, were considered to have ensured a source-to-drain withstand voltage property of each of transistors formed within the peripheral element region portion. Therefore, the channel stop ions have been injected only into the memory array region portion after the formation of the second well portion.
SUMMARY OF THE INVENTION
With the foregoing in view, it is therefore an object of the present invention to provide a semiconductor device capable of preventing deterioration in withstand voltage properties of elements formed in a peripheral element region portion.
It is another object of the present invention to provide a mask capable of preventing the concentration of impurities in active regions from excessively increasing and further simplifying a process for manufacturing a semiconductor device.
According to one aspect of the present invention, for achieving another object referred to above, there is provided a semiconductor device of the present invention, comprising:
a double well structure having a first well portion and a second well portion both of which are different in polarity from each other;
a semiconductor substrate whose surface common to the surfaces of the two well portions is partitioned into a plurality of active regions by field insulating films; and
a memory array region portion and a peripheral element region portion both formed within the second well portion,
whereby channel stop regions are formed within the memory array region portion and the peripheral element region portion by ion implantation.
According to another aspect of the present invention, for achieving another object referred to above, there is provided a mask comprising:
portions for respectively covering active regions lying within a second well portion;
portions for respectively covering edge portions of field insulating films adjacent to the active regions; and
openings through which channel stop ions can be injected below the field insulating films of a semiconductor substrate region excluding a first well portion.
Typical ones of various inventions of the present application have been shown in brief. However, the various inventions of the present application and specific configurations of these inventions will be understood from the following description.
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Booth Richard
Jones Volentine, LLC
OKI Electric Industry Co., Ltd.
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