Fabrication methods and structures are provided for the formation of monolithically isled back contact back junction solar cells. In one embodiment, base and emitter contact metallization is formed on the backside of a back contact back junction solar cell substrate. A trench stop layer is formed on the backside of a back contact back junction solar cell substrate and is electrically isolated from the base and emitter contact metallization. The trench stop layer has a pattern for forming a plurality semiconductor regions. An electrically insulating layer is formed on the base and emitter contact metallization and the trench stop layer. A trench isolation pattern is formed through the back contact back junction solar cell substrate to the trench stop layer which partitions the semiconductor layer into a plurality of solar cell semiconductor regions on the electrically insulating layer.