To realize a stable readout action in a memory cell of gain cell structure. The write-in transistor Qw of this invention comprises a source 2 and drain 3 formed on an insulating layer 6, channel 4 consisting of a semiconductor formed on the insulating layer 6 between the source 2 and drain 3, gate 1 that is formed at the upper part of the insulating layer 6 between the source 2 and drain 3 controls the electric potential of the channel 4 electrically insulated from the channel 4 through a gate insulating film 5. The channel 4 electrically connects the source 2 with the drain 3 through the side surface of the source 2 and drain 3. |