JPH0498872A - Semiconductor device - Google Patents

Abstract

PURPOSE:To enable transfer gate transistors provided in a lateral direction to be balanced in threshold voltage or to be protected against an offset phenomenon by a method wherein a capacitor electrode is provided partially overlapping the upper part of a transfer gate electrode. CONSTITUTION:First, an insulating film 10 is selectively formed on the surface of a semiconductor substrate 1 to demarcate an element region, and a gate insulating film 8 is provided onto the element region concerned. Then, transfer gate electrodes 11a and 11b are provided, and the surfaces of the electrodes 11a and 11b are covered with insulating films 12a and 12b respectively. Thereafter, impurity layers 13a, 13b, and 13c whose conductivity types are opposite to that of the semiconductor substrate 1 are provided, grooves 2a and 2b are engraved on the surface of the semiconductor substrate 1, and capacitor insulating films 15a and 15b are formed thereon. Then, capacitor electrodes 14a and 14b are built. Next, interlaminar insulating films 16a and 16b are provided, an opening 18 is bored, and then a wiring metal electrode 17 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device, and more particularly to a semiconductor device having a trench capacitor in a semiconductor substrate and a transfer gate electrode coupled to the trench capacitor.

[Conventional technology]

Conventionally, in order to improve the degree of integration of patterns without reducing the capacitance value, semiconductor devices have been created in which grooves are carved into the semiconductor substrate and the entire surface of the grooves is used as a capacitor. Later, an electrode that would become a transfer gate was placed on top of it.

FIG. 2 is a sectional view showing a conventional semiconductor device of this type. Grooves 2a and 2b are etched in the semiconductor substrate 1 by dry etching, capacitor insulating films 3a and 3b are formed on the surfaces of the grooves 2a and 2b, and a capacitor electrode 4 is further formed. Thereafter, transfer gate electrodes 5a and 5b are formed via insulating films 8a and 8b, and after forming an insulating film 6, wiring electrodes 7 are formed. This is a type of diffusion layer. In this way, the groove 2a,
Since the capacitor is formed using the surface of 2b, a high capacitance value can be obtained while maintaining a high degree of integration.

[Problem to be solved by the invention]

However, the semiconductor device mentioned above! In this case, since the transfer gate electrode is provided above the capacitor electrode, the following problem occurs.

FIGS. 3A and 3B are cross-sectional views showing the problem.

First, FIG. 3(a) shows a case where the end of the capacitor electrode 4 is shifted to the left. In this case, since the capacitor electrode 4 protrudes to the left from the diffusion layer 9b, an offset occurs, and the threshold voltage of the right transfer gate transistor becomes higher than that of the left transfer gate transistor. Otherwise, the ONL will disappear, and the circuit operation margin will become narrower, or the circuit will not operate normally.

Further, FIG. 3<b> shows transfer gate electrodes 5a, 5
It is a figure when b is shifted rightward. In this case, the effective channel lengths of the left and right transfer gate transistors become unbalanced, and the circuit operation margin becomes narrow or the circuit does not operate normally.

[Means to solve the problem]

In the semiconductor device of the present invention, the positional relationship between the capacitor tfi and the transfer gate pole is opposite to that of a conventional semiconductor device, and the capacitor electrode is provided with a portion of the capacitor electrode overlapping the transfer gate electrode.

In the present invention, since the capacitor electrode is arranged to overlap the top of the transfer gate electrode, it is possible to avoid the above-mentioned problem when either the capacitor electrode or the transagate electrode is misaligned. Problems such as imbalance in threshold voltage between left and right transfer gate transistors and offset phenomenon no longer occur.
This has particularly great advantages for finer patterns.

〔Example〕

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

FIGS. 1(a) and 1(b) are a plan view and a sectional view showing an embodiment of the present invention.

Grooves 2a and 2b are formed on the surface of a semiconductor substrate 1 made of silicon, etc., and a capacitive insulating film 15a is formed on the surface of the grooves 2a and 2b.
, 15b, and has a capacitive electrode 14 on its surface. Further, insulating films 12a, 1 are provided between the semiconductor substrate 1 and the capacitor electrode 14.
The transfer gate has poles 11a and 11b via 2b, and a wiring t[i17 is formed on top of the transfer gate via interlayer insulating films 16a and 16b.

The semiconductor device configured as described above is manufactured as follows.

4(a), (b) to FIG. 7(a>, (b) are diagrams arranged in the order of steps for explaining the manufacturing method of one embodiment of the present invention, and FIG. 4(a) ) to Figure 7 (a> is a plan view,
FIG. 4(b) to FIG. 7(b) are cross-sectional views.

As shown in FIGS. 4(a) and 4(b), an insulating film 1o is selectively formed on the surface of the semiconductor substrate 1 to define an element region, and a gate insulating film 8 is formed on the element region. Next, as shown in FIGS. 5(a) and (b), transfer gate electrodes 11a and 11b are provided, and then, as shown in FIGS. 6(a) and (b), transfer gate electrodes 11a and 11b are provided. Insulate the surface of llb! 12a, 12
Cover with b. Thereafter, impurity layers L3a and 13b13c of conductivity type opposite to that of the semiconductor substrate 1 are provided.

Next, as shown in FIGS. 7(a) and 7(b), the semiconductor substrate 1
Dip holes 2a and 2b are carved on the surface, and capacitive insulating films 15a and 15b are provided on the surface. After that, the capacitor electrode 14
b, 14b are provided.

Next, as shown in FIGS. 1A and 1B, interlayer insulating films 16a and 16b are provided, and after openings 18 are formed, wiring metal electrodes 17 are provided.

〔Effect of the invention〕

As explained above, in the present invention, a part of the capacitor tri is placed over the transfer gate electrode, so that either the capacitor electrode or the transfer gate electrode is misaligned, which is the problem mentioned above. This eliminates the imbalance of the threshold voltages of the left and right transfer gate transistors and the offset phenomenon, which would otherwise be a problem, and it becomes possible to make the semiconductor device uniform. This effect can be said to have a particularly great advantage in semiconductor devices with finer patterns.

[Brief explanation of the drawing]

1(a) and (b) are a plan view and a sectional view showing an embodiment of the present invention, FIG. 2 is a sectional view of a conventional semiconductor device having a capacitive part, and FIG. 3(a) and ( b) is a cross-sectional view showing an example of a defect in a conventional semiconductor device having a capacitive part;
FIGS. 4(a) to 7(b) are diagrams for explaining the manufacturing process of the semiconductor device of the present invention, and FIGS. a) is a plan view, Fig. 4(b)
-FIG. 7(b) is a sectional view. 1...Semiconductor substrate, 2a, 2b...-groove, 3a, 3b
... Capacitive part insulating film, 4... Capacitive part gate electrode, 5a
. 5b...Transfer gate electrode, 6...Interlayer insulating film, 7...Wiring ti, 8a, 8b...Transfer gate insulating film, 9a, 9b, 9c, 9d, 9e- anti-conductivity type to substrate Impurity layer, 10...insulating film, 11a, ll
b... Four transfer gate electrodes, 12a. 12 b--Insulating film, 13a, 13b, 13cm
Impurity layer opposite to the substrate, 14a, 14b... Capacitive part electrode, 15a, 15b... Capacitive part insulating film, 16a. 16b... Interlayer insulating film, 17... Wiring electrode.

Claims (1)

[Claims] In a semiconductor device having a groove capacitor in a semiconductor substrate and a transfer gate electrode coupled to the groove capacitor, a part of the capacitor electrode of the groove capacitor is provided above the transfer gate electrode in an overlapping manner. Characteristic semiconductor devices.