JPH0421958B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor memory device that can improve access time and reduce power consumption.

[Conventional technology]

FIG. 2 is a block diagram showing a conventional semiconductor memory device. In the figure, 1 is a memory cell arranged in a matrix, the detailed circuit of which is shown in FIG. 2, 2a and 2b are a pair of complementary bit lines, and 3 is a memory cell on the same row when selected. A word line for activating cell 1, 4 a row decoder for decoding row address information, 5 a row address signal line,
6a and 6b are bit line loads connected to the bit lines 2a and 2b, respectively, and 7 is a power supply terminal.

Note that in the memory cell 1 shown in FIG.
a and 8b are load elements composed of MOS transistors, resistors, etc.; 9a and 9b are inverter transistors; 10a and 10b are access transistors; 11a and 11b are memory cells 1
is a store node.

In addition, memory cell 1 is connected to bit lines 2a and 2b.
Since a direct current flows when reading information from the memory cell 1 and writing information to the memory cell 1, a voltage drop caused by this direct current and the resistance of the bit lines 2a and 2b has an adverse effect on the information reading and writing operations.
For example, aluminum, which has a low resistance, is generally used for the bit lines 2a and 2b, since this reduces the read and write speeds.

Further, the word line 3 is connected to the access transistors 10a and 1 of the memory cell 1 arranged in the corresponding row.
Generally, in order to reduce the memory cell area, the word line 3 and the gate electrodes of the access transistors 10a and 10b of the memory cell 1 arranged in the corresponding row are integrally formed. It used silicon.

Next, the operation of the semiconductor memory device with the above configuration will be described, as an example, in the case where store nodes 11a and 11b are written to "H" level and "L" level, respectively.
First, in the case of reading, when the address information of the cell to be read is inputted to the address signal line 5, the desired word line 3 is activated through the row decoder 4. When word line 3 is activated, access transistor 10b storing "L" level becomes conductive. Therefore, a current flows from the power supply terminal 7 through the path of the bit line load 6b, the bit line 2b, the access transistor 10b, and the inverter transistor 9b, allowing reading.

In a semiconductor memory device with this configuration, all memory cells on the same row are activated, so current flows from the power supply to the memory cells in all columns, and when configuring a large capacity static RAM with many columns, current consumption is reduced. growing. Therefore, in order to reduce current consumption, a semiconductor memory device shown in FIG. 4 has been proposed. In this case, the row decoder 4 is arranged in the center of the memory cell plane, the word line is divided into the left word line 3a and the right word line 3b, and only the word line of the selected memory cell group of the left and right memory cell groups is used. By activating
Current paths are generated only in half of all the columns. Note that 12a and 12b are AND gates that select the left word line 3a or the right word line 3b, respectively, and 13a and 13b are gate signal lines that open the AND gates 12a and 12b, respectively.

Next, FIG. 5 is a layout diagram showing a conventional semiconductor memory device constructed based on the idea of FIG. 4.
In this case, the row decoders 4a and 4b are arranged in a plurality of columns, and the word lines 3a to 3d are divided by a multiple thereof, thereby reducing the number of DC current paths.

[Problem that the invention seeks to solve]

However, conventional semiconductor memory devices require a large number of row decoders. For this reason,
This method had drawbacks such as an increase in chip area and a loss in speed performance and yield.

Furthermore, since the word line is made of relatively high-resistance polysilicon and is integrated with the gate electrode of the access transistor of the memory cell, there is also the problem that the access time for reading and writing becomes long. It was something I had.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a high-speed, large-capacity semiconductor memory device with low power consumption.

[Means for solving problems]

In order to achieve such an object, the present invention provides a plurality of memory cell groups in which a memory cell array in which memory cells are arranged in a matrix is divided and arranged in the column direction, and a memory cell array corresponding to each of the plurality of memory cell groups. a memory cell group selection line for selecting a specific one of each memory cell group; a row decoder for decoding the row address information of the memory cell group to be accessed; is activated based on the selection signal of the memory cell group selection line provided corresponding to each of the plurality of memory cell groups and the output signal of the front word line. The front word line is made of aluminum.

[Effect]

The semiconductor memory device according to the present invention has high speed and low power consumption.

〔Example〕

FIG. 1 is a block diagram showing one embodiment of a semiconductor memory device according to the present invention.
Memory cell groups 1a and 1b divided into three in the column direction
The case where 1c and 1c are arranged is shown. In the figure, 14a, 14b and 14c are memory cell group selection lines for selecting the memory cell groups 1a to 1c;
15 are word lines 3a to 3c as divided word lines.
Preword lines arranged in parallel in the same direction as 1
6a, 16b and 16c have input terminals connected to the front word line 15 and the memory cell group selection lines 14a to 16c, respectively.
14c, and the output terminals are connected to word line 3.
This is an AND gate connected to a to 3c.

Note that in order to reduce the memory cell area, the word lines 3a to 3c are formed of a polysilicon layer in the same layer as the gates of the MOS transistors 10a and 10b, and the pre-word lines 15 are these word lines 3a to 3c. An aluminum wiring layer separate from this polysilicon layer is formed.

Note that recently, in the semiconductor technology field, a technology has been established that allows the formation of two aluminum wiring layers, so the front word lines 3a, 3b, and 3c are replaced by the bit line 2.
It is now possible to form an aluminum wiring layer which is a layer separate from a and 2b.

Next, the operation of the semiconductor memory device with the above configuration will be explained. First, for example, memory cell group 1
When selecting a memory cell in a, the row address information of the memory cell group 1a to be accessed is decoded by the row decoder 4, and one of the front word lines 15 is activated. Then, when a selection signal is applied to the memory cell group selection line 14a, the AND gate 16a opens and the word line 3a is activated. Therefore, the column current flowing from the power source (not shown) to the memory cell group 1a through the bit line (not shown) flows only in the columns in the selected memory cell group 1a.

Note that although the selection of memory cells within the memory cell group 1a has been described above, selection of memory cells within the memory cell group 1a has been described;
Of course, the same can be done for b and 1c. Further, although the case where the memory cell group is divided into three cells has been described, it goes without saying that the same effect can be achieved even if the memory cell group is divided into N cells (N>2). Furthermore, if only the pre-word line 15 is made of a low-resistance material, even if the word line has a somewhat high resistance, the word line has a short length and therefore has a small capacitance, and the memory cells can be accessed at high speed. Also, and gate 1
Since the circuits 6a to 16c have two input terminals and one output terminal, the circuit configuration is simple, and the increase in chip area can be ignored. Furthermore, it goes without saying that the row decoder 4 may be placed at the center of the chip or at the edge of the chip. Furthermore, although the row decoders are arranged at the ends of the chips in the above embodiments, they may of course be arranged at the center of the chips.

As described above in detail, according to the semiconductor memory device according to the present invention, row selection is performed hierarchically such that memory cell selection is performed in two stages: front word line and word line. Since the number of columns with direct current paths in the columns can be reduced, it is possible to construct a high-speed, low power consumption, large-capacity semiconductor memory device.

〔Effect of the invention〕

As explained above, in the present invention, the number of columns with DC current paths can be reduced by performing memory cell selection in two stages: pre-word lines and divided word lines. This has the effect of making it possible to obtain a high-speed, low-power consumption, large-capacity semiconductor memory device.

Furthermore, since the front word line is made of aluminum, the resistance of the front word line extending over a plurality of memory cell groups is reduced, and access time can be increased.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a semiconductor memory device according to the present invention, FIG. 2 is a detailed circuit diagram of a memory cell, FIG. 3 is a block diagram showing a conventional semiconductor memory device, and FIG. 4 is a block diagram showing an embodiment of a semiconductor memory device according to the present invention. FIG. 5 is a block diagram showing another conventional semiconductor memory device, and FIG. 5 is a layout diagram showing another conventional semiconductor memory device. 1a to 1c... memory cell group, 3a to 3c...
Word line, 4...Row decoder, 14a-14c...
...Memory cell group selection line, 15...Previous word line,
16a-16c...and gate.

Claims (1)

[Scope of Claims] 1. A plurality of memory cell groups in which a memory cell array in which memory cells are arranged in a matrix is divided into a plurality of blocks in the column direction, and a plurality of memory cell groups are provided corresponding to each of the plurality of memory cell groups. A memory cell group selection line for selecting a specific one of each memory cell group, a bit line connected to a plurality of memory cells arranged in a corresponding column in the memory cell group, and a memory cell group to be accessed. a row decoder for decoding row address information of the row decoder; a preword line connected to the output terminal of the row decoder and arranged across the plurality of memory cell groups; A divided word line is provided and activated based on a selection signal of the memory cell group selection line and an output signal of the pre-word line, the divided word line is formed of polysilicon, and the bit line is 1. A semiconductor memory device characterized in that the semiconductor memory device is made of aluminum, and the front word line is made of aluminum located in a layer different from the bit line.