JPS59125654A - Semiconductor device - Google Patents

Abstract

PURPOSE:To protect a condenser which uses the first capacity unit in a semiconductor device which employs a capacitor and a field effect transistor as an information memory unit by providing the second capacity unit having an insulating layer of low insulating withstand strength. CONSTITUTION:A field effect transistor operates as source and drain at an impurity diffused layer 2 and an inversion layer 3, and constructs as a gate the second conductive layer 6 through the gate insulating film 7 of dioxidized silicon film. The first capacity unit I is formed of the layer 6 and the first conductive layer 5 through a dielectric layer 8 of dioxidized silicon film, and the second capacity unit II is formed between the second conductive layer 6 through a dioxidized silicon film 9 thinner than the region I and an inversion layer 3'. If charge is induced at the layer 5, an insulation breakdown occurs in the second unit II weaker in the insulating withstand strength, the charge of the layer 5 flows to a semiconductor substrate 1, the charge-up more than it is prevented, and the first unit I which operates as the information memory section is protected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device, particularly a semiconductor device in which a capacitor having a thin insulating film and a field effect transistor are used as information storage units.

1 (The so-called one-transistor memory cell, which is composed of an FFLL capacitor and one transistor, is used as the most common storage unit for large-capacity memory, but as technology advances toward larger capacity and higher integration, With the progress of miniaturization year by year, the amount of space required for one piece of content has been forced to decrease.

However, it is necessary to ensure a sufficient capacitance value required for information storage, and as a result, the insulating film between the opposite electrodes of the capacitor has to become thinner and thinner.

However, a thinner insulating film has a lower dielectric strength.
If the conductive layer, which is one opposite electrode of the capacitor, is electrically insulated from the semiconductor substrate, for example, if charge-up occurs and charges are induced on the conductive layer,
Dielectric breakdown is likely to occur in a part of the capacitor of the memory cell, which is the weakest point. Once dielectric breakdown occurs and a short circuit occurs with the semiconductor substrate, no further charge-up occurs, but if dielectric breakdown occurs even in one place, other memory cells may be operating normally. However, due to that one bit defect, the function as a semiconductor device will be impaired.

Non-invention is a solution to such inconveniences.

The uninvented structure is a semiconductor in which an information storage unit is composed of a field effect transistor formed on a semiconductor substrate and a content that uses a first capacitor section having one or more insulating layers for at least part of charge storage. In the apparatus, part of the conductive layer including one counter electrode of the first capacitive part is made of gold as one counter electrode, and the insulating layer and the silicon of the first capacitive part are formed in a region other than the capacitive part of the hole 1. This semiconductor device is characterized by having an M2 capacitor portion having an insulating layer with a low dielectric strength voltage.

Next, a detailed explanation of the invention will be given with reference to the drawings. FIG. 4 shows an embodiment of the invention.

In Figure 1, 1 is a semiconductor substrate, 2 is an impurity diffusion layer in which impurities of the opposite conductivity type to the substrate are diffused, 3 is an inversion layer, 4 is an insulating layer composed of a silicon dioxide film, and 5 is an impurity doped layer. The 1ffi conductive layer is made of polycrystalline silicon, and 6 is the second conductive layer made of polycrystalline silicon doped with impurities. In the field effect transistor, an impurity diffusion layer 2 and an inversion layer 3 function as a source/drain, and a second conductive layer 6 with a gate insulating film 7 of silicon dioxide film interposed therebetween serves as a gate. The first capacitor section is constituted by an inversion layer 6 and an IN-th conductive layer 5 with a dielectric film 8 of a silicon dioxide film interposed therebetween, and is a region indicated by I in the figure. In the figure, a region indicated by a square mark is a second capacitor section formed between the second conductive layer N6 and the inversion layer 3' via a silicon dioxide film 9 which is thinner than the region marked by a square mark. Figure 1 shows the state in the middle of the wafer processing process, but if charges were to be induced in the first conductive layer in this state, the second capacitive part in the region (■) where the dielectric strength voltage is weaker would be dielectric breakdown occurs. As a result, the charges in the IN-th conductive layer flow into the semiconductor substrate, and further charge-up is prevented, and the first capacitor section in region I, which functions as an information storage section, is protected.

By the way, it is known that dielectric breakdown in this second capacitor part occurs in the form of a pinhole at a weak point, and although the resistance is low enough to allow the charge in the conductive layer to flow to the substrate side after dielectric breakdown, the semiconductor When a voltage necessary for the operation of the semiconductor device is applied between the first conductive layer 5 and the semiconductor substrate after the device is completed, the resistance can be made sufficiently large so that the current flowing between the two does not exceed the standard. It is not necessary to provide this second capacitance section for each unit cell; it is sufficient to provide at least one second capacitance section for one continuous plane of the first conductive layer 5. Needless to say.

[Brief explanation of drawings]

FIG. 1 is an intermediate view of a semiconductor device according to an embodiment of the present invention. It shows the structure of the process. Each part has the following conventions. 1... Semiconductor substrate, 2... Impurity diffusion layer of conductivity type opposite to that of the substrate, 3... Inversion layer, 4...
・Insulating layer (field insulating layer) such as silicon dioxide film,
5...First conductive layer, 6...Second conductive layer, ■...First capacitor section, ■...Second conductive layer
capacitive part, 7...gate insulating film, 8...
- Dielectric film of the first capacitive part, 9... Dielectric film of the second capacitive part.

Claims (1)

[Claims] In a semiconductor device in which an information storage unit is constituted by a field effect transistor formed on a semiconductor substrate and a capacitor that uses a first capacitance section having one or multiple insulating layers for at least part of charge storage, the first A part of the conductive layer including one counter electrode of the capacitive part is used as one counter electrode, and an insulating layer having a lower dielectric strength voltage than the insulating layer of the first capacitive part is provided in a region other than the first capacitive part. A semiconductor device comprising a second capacitor section.