Semiconductor memory device having a plurality of transfer gates and improved word line and column select timing for high speed write operations

Abstract

A semiconductor memory device which receives a row address strobe (RAS) signal and a column address strobe (CAS) signal from an external device. The device includes rewritable memory cells formed on a semiconductor substrate, a plurality of bit lines, a plurality of word lines, and a transfer gate coupled between the bit lines and input/output (I/O) lines and controlled by a column select line or signal. In one embodiment, a first transfer gate is connected between the bit lines and a second transfer gate, the second transfer gate connected between the first transfer gate and an input/output (I/O) line and controlled by a column select line (CSL). A third transfer gate may also by provided. The first transfer gate is driven in response to a clock signal which is enabled at substantially the same time as a word line of the plurality of word lines is selected during both read and write cycles. Thus, during a write cycle in which the CAS signal is enabled prior to the RAS signal, a selected CSL can be increased from a first voltage (VSS) to one of a second voltage (Vdd) and {fraction (3/2)} Vdd as soon as a column address is input.