a lateral bipolar transistor affording a good controllability for a base length is disclosed . in fabricating a lateral bipolar transistor by forming a single crystal column and disposing heavily doped polycrystalline regions on both sides of the column , contact surfaces between the single crystal column and the heavily doped polycrystalline regions are controlled by etching of an oxide film . the etching of the oxide film can provide a device of a precision higher than attained by controlling any other element .