A method for forming a semiconductor device includes forming a first semiconductor layer over a substrate, forming a first photoresist layer over the first semiconductor layer, and using only a first single mask patterning the first photoresist layer to form a first patterned photoresist layer. The method further includes using the first patterned photoresist layer etching the first semiconductor layer to form a select gate and forming a charge storage layer over the select gate and a portion of the substrate. The method further includes forming a second semiconductor layer over the charge storage layer, forming a second photoresist layer over the second semiconductor layer, and using only a second single mask patterning the second photoresist layer to form a second patterned photoresist layer. The method further includes forming a control gate by anisotropically etching the second semiconductor layer and then subsequently isotropically etching the second semiconductor layer.