JPS5858747A - Metal oxide semiconductor type semiconductor integrated circuit - Google Patents

Abstract

PURPOSE:To prevent the generation of a parasitic MOSFET by forming a semiconductor layer, which is electrically connected to a semiconductor substrate and to which fixed voltage is applied, between an electrode functioning as the gate electrode of the parasitic MOSFET and the silicon substrate section just under the electrode. CONSTITUTION:A fixed potential electrode 16 is formed into a field oxide film positioned onto the silicon substrate section 15, and the one part 16' is connected to the silicon substrate. According to such constitution, the generation of the parasitic MOSFET is prevented because the electrode 13 has no effect on the silicon substrate section 15. The width l1 of the fixed potential electrode 16 is not limited particularly, and may be equal to the width l2 of the silicon substrate section 15.

Description

[Detailed Description of the Invention] The present invention relates to an MO3 type semiconductor integrated circuit, and a parasitic MO8)
The present invention provides a MOS transistor structure that can prevent the generation of transistors.

Mo8) In an MO8 semiconductor integrated circuit configured using transistors as circuit elements, parasitic MoS transistors may occur between built-in MoS transistors.

The figure below shows that such parasitic MO8) transistors are rooted, 2,
3 is the drain and source region of the first MOS transistor, 4 and 6 are the drain and source regions of the second MOS transistor, 6°7 is the gate oxide film, 8°, 9
10 is a gate electrode, 10 is a field oxide film, and 11 is a gate electrode.
．． 12, 13 and 14 are electrodes. By the way, as shown in the figure, if the electrode 13 extends to the field oxide layer located between the first MOS transistor and the second Mo8 transistor, when a voltage is applied to the electrode 13, , this field is where a parasitic MOS transistor is generated whose channel is the silicon substrate portion 15 directly below the oxide film.

In order to prevent the generation of this parasitic MOS transistor, 3-2 conventionally, impurities of the same conductivity type as the silicon substrate are diffused into the silicon substrate portion 15 to form a high impurity concentration layer;
Alternatively, measures have been taken such as making the field oxide film on the silicon substrate portion 16 sufficiently thick so that the influence of the voltage of the electrode 13 does not reach the silicon substrate portion 15.

The present invention provides a structure that can be newly added to one of these countermeasures, and its characteristics are as follows:
8) A semiconductor layer or a semiconductor layer electrically connected to the semiconductor substrate at at least one point and to which a predetermined fixed voltage is applied between the electrode that acts as the gate electrode of the transistor and the silicon substrate portion immediately below the electrode. This is where a fixed potential electrode made of a semiconductor layer is provided.

FIG. 2 is a diagram illustrating a cross-sectional structure of a main part of an MO8 type semiconductor integrated circuit according to an embodiment of the present invention constructed by applying the present invention, and the same reference numerals are given to the parts opposite to those in FIG. 1. As shown in the figure, a fixed potential electrode 16 is provided in a field oxide film located on a silicon substrate portion 15, and a portion 16' thereof is connected to the silicon substrate. There is a difference between With such a structure, the influence of the electrode 13 no longer reaches the silicon substrate portion 16, and the generation of this parasitic MO3) transistor is prevented. Note that there is no particular restriction on the width e1 of the fixed potential electrode 16;
50 width g2. Further, the width may be even narrower than the width shown in the drawings.

In order to confirm the effect of the present invention explained above, e2 was
Fixed potential electrode 15, electrode 3 and silicon substrate portion 15
The structure of the present invention in which the thickness of the silicon dioxide film between the electrodes 13 and 13 is 600° and 300°, and the fixed potential electrode is eliminated and the thickness of the silicon dioxide film directly under the electrode 13 is 6300°
The conventional structure with a resistivity of 8 and 8" has a resistivity of "6'.
・cm (7) tj A N-type 7 silicon substrate was obtained as a starting material, a negative voltage was applied to the electrode, and it was examined at what voltage a parasitic MOS transistor was generated.

In the present invention, parasitic MO8) is generated when a negative voltage of about 50V is applied.
A transistor is generated. In contrast, in the conventional structure, approximately s
It was confirmed that a parasitic MO8 transistor was generated by applying a negative voltage of oV, and that there was a clear difference between the two.

From the above explanation, it is clear that the M of the present invention
In the O8 type semiconductor integrated circuit, the generation of parasitic MO3, ) transistors can be effectively prevented, and inconveniences such as malfunctions can be eliminated. Although the above description has been made using an N-type silicon substrate as a starting material, it goes without saying that the present invention is also applicable to a case where a P-type silicon substrate is used.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the conventional structure of a MO8 type semiconductor integrated circuit where two transistors are close to each other, and FIG. 2 is a cross-sectional view showing the structure of an MO3 type semiconductor integrated circuit according to an embodiment of the present invention. It is a diagram. -1...Silicon substrate, 214...Drain region, 3,6...
...Source electrode, 6, 7... Gate oxide film, 8, 9, ..., Gate electrode, 10...
... Field oxide film, 15 ... Silicon substrate part for separation, 16 ... Fixed-position electrode, 16
′...Fixed potential electrode part connected to silicon/substrate part.

Claims (1)

[Claims] A first Mo8) transistor is fabricated in a predetermined area of a semiconductor substrate, a second Mo8) transistor is fabricated in the substrate adjacent to the first Mo8) transistor, and a second Mo8) transistor is fabricated in the substrate in the vicinity of the first Mo8) transistor;
O8) There is a structural part in which a wiring layer to which a predetermined voltage is applied is formed on the upper side of the insulating film covering the isolation semiconductor substrate region located between the transistors, and between the wiring layer and the insulating film. An MO8 type semiconductor integrated circuit, further comprising a conductive layer or a semiconductor layer connected to the semiconductor substrate at at least one point and to which a predetermined fixed voltage is applied.