A semiconductor memory device includes a plurality of wordline driving circuits adapted to control the voltage level of a sub-wordline in response to a logic state of a global wordline and an address signal. The wordline driving circuit comprises first and second transistors configured to maintain the sub-wordline at a first voltage level when the global wordline and the address signal have a first logic state and at a second voltage level when the global wordline or the address signal have a second logic state.

Read disturbs in phase change memories may be reduced by progressively reducing the read pulse falling edges. This may reduce the possibility of quenching and inadvertent amorphization of at least a portion of the bit. As a result, in some embodiments, read disturbs may be reduced.

Disclosed is a phase-changeable memory device and a related method of reading data. The memory device is comprised of memory cells, a high voltage circuit, a precharging circuit, a bias circuit, and a sense amplifier. Each memory cell includes a phase-changeable material and a diode connected to a bitline. The high voltage circuit provides a high voltage from a power source. The precharging circuit raises the bitline up to the high voltage after charging the bitline up to the power source voltage. The bias circuit supplies a read current to the bitline by means of the high voltage. The sense amplifier compares a voltage of the bitline with a reference voltage by means of the high voltage, and reads data from the memory cell. The memory device is able to reduce the burden on the high voltage circuit during the precharging operation, thus assuring a sufficient sensing margin during the sensing operation.

A method and device for driving the word lines of a phase change memory device is provided. The method may include applying a first voltage level to non-selected word lines and a second voltage level to selected word lines during a normal operational mode, and placing the word lines in a floating state during a standby operational mode. The phase change memory device may include a plurality of word line drive circuits for driving corresponding word lines, where each of the plurality of word line drive circuits includes a drive unit which sets a corresponding word line to a first voltage level or a second voltage level in response to a first control signal, and a mode selector which selectively applies the first voltage level to the driving unit according to an operational mode of the phase change memory device.

The invention includes an apparatus and method of selecting memory cells within a memory array. The method includes receiving a memory cell address. A column address and a row address are generated from the memory cell address. Row select lines or column select lines are pre-charged. A self-timed charging circuit is initiated to provide an adequate amount of time to charge a selected row, and to initiate elimination of static current flowing to unselected rows after a self-timed delay. The other of the row select lines or the column select lines are then pre-charged. Memory cells are selected based upon the column address and the row address. One of two states of the memory cells can be based upon sensing threshold voltages of sense lines that correspond with the selected memory cells.