Method for Forming a Semiconductor Device Structure

A method for forming a semiconductor device structure includes forming a layer stack comprising alternating sacrificial layers of a first semiconductor material and channel layers of a second semiconductor material. The method includes forming over the layer stack a plurality of parallel and regularly spaced core lines and forming spacer lines on side surfaces of the core lines. The method includes forming first trenches extending through the layer stack by etching the layer stack while using the core lines and the spacer lines as an etch mask and forming insulating walls in the first trenches and in the gaps by filling the first trenches and the gaps with insulating wall material. The method also includes forming second trenches extending through the layer stack by etching the layer stack while using the spacer lines and the insulating walls as an etch mask, thereby forming a plurality of pairs of fin structures.