A method of manufacturing a semiconductor device including providing a first layer, forming a layer of stacked oxide-nitride-oxide layer over the first layer, depositing a first silicon layer over the layer of stacked oxide-nitride-oxide layer, providing a layer of photoresist over the first silicon layer, patterning and defining the photoresist layer, etching the first silicon layer and stacked oxide-nitride-oxide layer unmasked by the photoresist, removing the photoresist layer, providing a cleaning solution to the stacked oxide-nitride-oxide layer with the first silicon layer as a mask, and depositing a second layer of polysilicon over the first silicon layer to form a combined silicon layer.