In a multi-pole connector formed by combining a plurality of connector housings together, a bolt and a bolt receiving tube are provided at first connector housing, and a frame portion is formed on the second connector housing. This invention also relates to inbred corn lines derived from inbred corn line MEA01, to methods for producing other inbred corn lines derived from inbred corn line MEA01 and to the inbred corn lines derived by the use of those methods. An avalanche breakdown occurs under the bottom of the base diffusion region, and the avalanche current is not passed through a high resistance part immediately under the source diffusion region in the base diffusion region, thereby providing high withstand strength against destruction. A hard mask layer is formed on the metal layer.