JPH06350047A - Semiconductor memory device - Google Patents

Abstract

PURPOSE:To increase cell capacitance without increasing the cell area. CONSTITUTION:In a laminated substrate electrode 1 which forms a memory capacitor, its top face is so shaped that the outer periphery may be longer despite of the same area as in the prior art. This can increase the side face area of the substrate electrode, thereby increasing the memory cell capacitance Cs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor memory device, and more particularly to the shape of a substrate electrode forming a memory capacitor portion.

[0002]

2. Description of the Related Art Referring to FIG. 5 showing a conventional stack type semiconductor memory device, this device has a substrate electrode 1, a capacitance insulating film 2, a capacitance electrode 3, a lead electrode 4, and an N type diffusion layer 5. And the semiconductor substrate 6, and the memory capacitance portion is formed between the substrate electrode 1 and the capacitance electrode 3.

The substrate electrode 1 shown in FIG. 5 has a combined shape of two square poles as shown in the perspective view of FIG.
The upper surface of the substrate electrode 1, that is, the portion of dimension A × B in FIG. 7 is a quadrangle.

In conventional stacks and semiconductor memory devices,
As shown in the plan view of FIG. 6, a large number of substrate electrodes 1 having the shape shown in FIG. 7 are regularly arranged on the main surface of the semiconductor substrate 6.

[0005]

With the shape of the substrate electrode 1 of the conventional semiconductor memory device described above, the capacitance insulating film 2 is used when the capacitance of the memory capacitance portion is increased in order to improve the characteristics and reliability of the device. If the film thickness is constant, the upper surface area of the substrate electrode 1 (dimension A × B in FIG. 7) is increased, or the side surface height of the substrate electrode 1 (dimension C in FIG. 7)
However, the former configuration has a drawback that the chip area is large, and the latter configuration has a drawback that the manufacturing conditions are strict because the step difference after forming the substrate electrode 1 is large.

[0006]

The structure of a semiconductor memory device of the present invention is characterized in that it is provided with a substrate electrode having a 2n square upper shape.

[0007]

1 is a plan view showing the arrangement of substrate electrodes according to the first embodiment of the present invention, and FIG. 2 is a perspective view showing the shape of the substrate electrodes. By refracting the pair of upper side surfaces facing each other in the same direction (here, in the shape of an arrow blade), the side surface area is large even if the upper surface area of the substrate electrode 1 is constant. The upper surface has a hexagonal shape.

Further, as shown in FIG. 1, since the substrate electrodes 1 are regularly arranged, the chip area is constant even with this shape. Note that the description of FIG. 5 is omitted because it is common.

Referring to the plan view of FIG. 3 showing the arrangement of the substrate electrodes of the second embodiment of the present invention, and the perspective view of FIG. 4 showing the shape of the substrate electrodes, this embodiment shows a center bent arrow blade shape. It has an octagonal shape of the upper part of the substrate electrode 1, and by refracting two sets of facing side faces in the same direction, the side face area is smaller than that of FIG. growing.

Further, as shown in FIG. 3, the substrate electrode 1 is
Since they are arranged regularly, the chip area is constant. Therefore, the second embodiment can obtain the effects more than those of the first embodiment. Further, in the first embodiment, one pair of side surfaces facing each other is refracted in the same direction, whereas in the second embodiment, two pairs of side surfaces facing each other are refracted in the same direction. The side surface area can be increased as compared with the first embodiment.

Thus, the top surface shape of the substrate electrode 1 is 2
If it is an n (n is an integer of 3 or more) polygon, the side surface area can be increased without increasing the entire chip area as shown in FIGS.

[0012]

As described above, according to the present invention, since the side surface area of the substrate electrode is increased and the substrate electrodes are regularly arranged, the chip area, the upper surface area and the height of the substrate electrode can be increased. This has the effect of increasing the capacity of the memory cell capacity section.

[Brief description of drawings]

FIG. 1 is a plan view showing an arrangement of substrate electrodes according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing the shape of a substrate electrode according to the first embodiment of the present invention.

FIG. 3 is a plan view showing an arrangement of substrate electrodes according to a second embodiment of the present invention.

FIG. 4 is a perspective view showing a shape of a substrate electrode according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view showing the structure of a memory cell.

FIG. 6 is a plan view showing an arrangement of conventional substrate electrodes.

FIG. 7 is a perspective view showing the shape of a conventional substrate electrode.

[Explanation of symbols]

 1 substrate electrode 2 capacitance insulating film 3 capacitance electrode 4 gate electrode 5 N type diffusion layer 6 semiconductor substrate

Claims (1)

[Claims] 1. In a semiconductor memory device in which a memory capacitor portion is formed by laminating a capacitor electrode on a substrate electrode on a semiconductor substrate with an insulating film interposed therebetween, the substrate electrode comprises:
A semiconductor memory device having a 2n (n is an integer of 3 or more) rectangular upper shape.