Abstract: A direct sense amplifier of the present invention incorporates and isolates: an MOS transistor serving as a differential pair and having a gate connected to a bit line; and an MOS transistor controlled by a column select line wired between RLIO lines in a bit-line direction, and further connects a source of the MOS transistor serving as the differential pair to a common source line wired in the word-line direction. Since the direct sense amplifier only in a select map is activated by the column select line and the common source line during an read operation, power consumption is significantly reduced during the read operation. Also, since a parasitic capacitance of the MOS transistor serving as the differential pair is separated from the local IO line, a load capacity of the local IO line is reduced and the read operation is speeded up. In addition, during the read operation, a data pattern dependency of the load capacity of the local IO line is reduced and a post-manufacture test is easily made.

Abstract: P-type well regions Ap1 and Ap9 on which first and second pre-charge circuits are formed, and p-type well regions Ap2, Ap3, Ap7 and ap8 on which first and second Y-switch circuits are formed, are formed on both ends of a sense amplifier formation region, respectively. A bit line BL2T, which extends from a first memory cell formation region of first and second memory cell formation regions arranged in both sides of the sense amplifier formation region, arrives at a p-type well region An1 on which a sense amplifier is formed, via both a p-type well region Ap1 on which the first pre-charge circuit is formed and p-type well regions Ap2 and Ap3 on which the Y-switch circuit is formed. Therefore, a wiring region c for arranging wirings other than bit lines can be secured on the extended bit line BL2T.