Semiconductor memory device with a reference or dummy cell for testing
A semiconductor memory device includes: memory cells respectively arranged on intersecting points of a plurality of word lines and a plurality of data lines, and respectively having a capacitor for storing data; a sense amplifier provided in between the data lines forming a data line pair so as to amplify an electric potential difference between the data lines and to perform data reading; and a test memory cell arranged on each of the data lines and having a test capacitor with a capacitance value set smaller than the above capacitor, and when performing a test for a memory cell, inversed data of the data to be stored into a target memory cell of a test target is pre-written into the test memory cell.
1. A semiconductor memory device comprising:
memory cells respectively arranged on intersecting points of a plurality of word lines and a plurality of data lines, and respectively having a capacitor for storing data;
a sense amplifier provided in between said data lines forming a data line pair, so as to amplify an electric potential difference between said data lines and to perform data reading; and
a test memory cell arranged on each of said data lines and having a test capacitor with a capacitance value set smaller than that of said capacitor,
wherein when performing a test for said memory cells, inversed data of the data to be stored into a target memory cell of a test target is pre-written into said test memory cell.
2. A semiconductor memory device according to claim 1 , further comprising a test word line driver activating a test word line that selects a test memory cell arranged on a data line to which said target memory cell is connected so as to correspond to a word line selection of said target memory cell, when performing a capacitor capacitance value test for said target memory cell.
3. A semiconductor memory device according to claim 2 , further comprising a control section stopping a selection operation of a row decoder that activates a word line of said memory cell, when writing data into said test memory cell.
4. A semiconductor memory device according to claim 1 , wherein said test capacitor is set so as to have a capacitance value of a capacitor to be detected as a defective cell.
5. A semiconductor memory device according to claim 2 , wherein in order to perform said capacitor capacitance value test for said target memory cell, then when said target memory cell and said test memory cell that corresponds to said target memory cell are read at the same time,
said target memory cell is determined as a normal memory cell if said sense amplifier has outputted data stored in said target memory cell, and on the other hand, said target memory cell is determined as a defective memory cell if said sense amplifier has outputted data stored in said test memory cell.