Abstract: A device is provided for producing a crystallized silicon body for solar cells. The device includes a reaction vessel, a silicon container arranged within the reaction vessel for containing a raw silicon material, an upper heater arranged above the silicon container for heating the raw silicon material contained in the silicon container, a lower heater arranged below the silicon container for heating the raw silicon material contained in the silicon container, and an insulator unit arranged inside the reaction vessel for surrounding the silicon container, the upper heater and the lower heater. The insulator unit is provided with a side insulator which includes a fixed side insulation member, a plurality of movable side insulation members coupled with the fixed side insulation member and a plurality of side actuators operatively connected to the movable side insulation members for moving the movable side insulation members toward or away from the silicon container.