JPH0434962A - Semiconductor device - Google Patents

Abstract

PURPOSE:To improve reliability in writing of memory contents by implanting an N-type diffusing region for a P-N junction type diode to a part beneath a field oxide film before N-type impurities grow, and forming the peripheral part of the P-N junction so that the peripheral part extends into a part beneath a field oxide film. CONSTITUTION:An N-type diffused region 4 having the same concentration as that of material for forming a source or a drain is selectively provided on the surface of a P-type silicon substrate 9. Then, a channel stopper layer 3 and a field oxide film 2 are selectively formed so that a part of the field oxide film 2 is overlapped with the N-type diffused region 4. With the field oxide film 2 as a mask, N-type impurity ions are implanted, and N<+> diffused region 5 which is connected to the N-type diffused region 4 is formed. At this time, the P-N junction of a P-N junction type diode is formed of the channel stopper layer 3 and the N-type diffused region 4. The peripheral part of the P-N junction is formed so that the peripheral part extends into a part beneath the thick field oxide film 2. In this way, a stable reference high voltage for a memory characterized by high reliability and high durability is obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to semiconductor devices, and in particular to a PN inserted in the reverse direction for controlling the reference voltage of a memory that requires high voltage when writing memory contents on a semiconductor chip. Regarding the structure of a junction diode.

[Conventional technology]

Conventionally, the control of high voltage for writing memory contents has been achieved by connecting a P-type semiconductor substrate to the low potential side, and connecting an N-type region formed on the P-type semiconductor substrate for forming a source or drain to the high voltage side for writing memory contents. is connected to form a PN junction diode, and its breakdown voltage suppresses the upper limit of the write voltage.

FIG. 2 is a sectional view of a conventional semiconductor device.

As shown in FIG. 2, P+
type channel stopper layer 3 and thick field oxide film 2
After selectively forming the field oxide film 2, the field oxide film 2 is used as a mask to implant N-type impurity ions at the same concentration as that for forming the source or drain, so memory contents can be written only under the thin thermal oxide film 1. There is an N1 type diffusion region 5 of a diode for voltage control.

The PN junction of the PN junction diode is formed between a P1 type channel stopper layer 3 having a higher concentration than the P type silicon substrate 9, which is formed on the surface of the P type silicon substrate 9 before the field oxide film 2 is grown thickly, and an N" type channel stopper layer 3. Since it is formed in the diffusion region 5, the PN junction exists under the boundary between the thin thermal oxide film 1 and the thick field oxide film 2.

[Problem to be solved by the invention]

In this conventional semiconductor device, since the PN junction exists under the boundary between the thin thermal oxide film and the thick field oxide film, there are variations in the concentration of the P+ type channel stopper layer and the N+ type diffusion region in that part. , the stability of the breakdown voltage of the reverse bias of the PN junction diode deteriorates due to the modulation of the surface concentration due to the trapping of carriers in the thin thermal oxide film. There is a problem in that the reliability of memory content writing becomes low because the reference high voltage for writing memory content changes greatly afterwards.

[Means to solve the problem]

In the semiconductor device of the present invention, thick field oxidation is applied to the N-type diffusion region of a PN junction diode on a P-type semiconductor substrate inserted in the reverse direction for controlling a reference high voltage of a memory that requires a high voltage when writing memory contents. Before forming the film, N-type impurities with a concentration equivalent to that for forming the source or drain are implanted to the bottom of the field oxidation layer before the film is grown, thereby forming a PN junction of the diode in contact with the P+ type channel stopper layer. is formed by extending the peripheral edge of the field under a thick field oxide film.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view of one embodiment of the present invention.

As shown in FIG. 1, an N-type diffusion region 4 with a concentration equivalent to that forming a source or drain is selectively provided on the surface of a P-type silicon substrate 9, and then a channel stopper layer 3 and a field oxide film are formed. 2 is selectively formed so as to partially overlap with the N-type diffusion region 4. Next, using the field oxide film 2 as a mask, N type impurities are ion-implanted to form an N1 type diffusion region 5 connected to the N type diffusion region 4.

Here, the PN junction of the PN junction diode is formed by the channel stopper layer 3 and the N type diffusion region 4, and the peripheral portion of the PN junction is formed extending under the thick field oxide film 2.

〔Effect of the invention〕

As explained above, the present invention provides a method for attaching the periphery of the PN junction of a PN junction diode inserted in the reverse direction under a thick field oxide film to control the reference high voltage of a memory that requires a high voltage when writing memory contents. By forming the 21-type channel stopper region at the PN junction so that the PN junction is not affected by the thin thermal oxide film or the boundary between the thin thermal oxide film and the thick field oxide film, By making it difficult to cause variations in concentration in the N-type and N-type diffusion regions and eliminating surface concentration variations due to carrier trapping in the thin thermal oxide film, a stable reference high voltage for memory with high reliability and durability can be obtained. effective.

Further, the same effect can be obtained even if the PN junction diode according to the present invention is used for voltage control of parts other than memory.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 2 is a sectional view of an example of a conventional semiconductor device. 1... Thin thermal oxide film, 2... Field oxide film, 3
P+ type channel stopper layer, 4... N type diffusion region, 5... N+ type diffusion region, 6... Contact hole, 7... Ground potential or low potential metal conductor, 8...
...P+ type diffusion region for substrate contact, 9...P type silicon substrate, 10...high potential metal conductor, 11...
Interlayer insulation film.

Claims (1)

[Claims] In a semiconductor device having a PN junction diode inserted in the opposite direction for controlling a reference high voltage of a memory that requires a high voltage when writing memory contents, the periphery of the PN junction of the diode is located under a thick field oxide film. A semiconductor device characterized in that it is formed in an extended manner.