A method includes patterning a substrate to form a nanowire over the substrate, applying a plurality of doping processes to the nanowire to form a first drain/source region at a lower portion of the nanowire, a second drain/source region at an upper portion of the nanowire and a channel region, wherein the channel region is between the first drain/source region and the second drain/source region, depositing a first dielectric layer along sidewalls of the channel region, depositing a control gate layer over the first dielectric layer, wherein the control gate layer surrounds a lower portion of the channel region, depositing a second dielectric layer along the sidewalls of the channel region and over the control gate layer and forming a floating gate region surrounding an upper portion of the channel region.