A semiconductor device includes a differential sense amplifier connected to a bit line, and a data transfer circuit including a column selection switch for turning ON/OFF the connection between a data line and the bit line. The semiconductor device incorporates one of the following features: the on-state resistance of the column selection switch being higher than that of a transistor array of the differential sense amplifier; separate provision of two column selection switches, one for read operation and the other for write operation; provision of a bit line additional capacitance and a connection control switch therefor; and provision of a data line dividing switch.