A semiconductor device includes a first conductive layer on a semiconductor substrate, a dielectric layer including a high-k dielectric material on the first conductive layer, a second conductive layer including polysilicon doped with P-type impurities on the dielectric layer, and a third conductive layer including a metal on the second conductive layer. In some devices, a first gate structure is formed in a main cell region and includes a tunnel oxide layer, a floating gate, a first high-k dielectric layer, and a control gate. The control gate includes a layer of polysilicon doped with P-type impurities and a metal layer. A second gate structure is formed outside the main cell region and includes a tunnel oxide layer, a conductive layer, and a metal layer. A third gate structure is formed in a peripheral cell region and includes a tunnel oxide, a conductive layer, and a high-k dielectric layer having a width narrower than the conductive layer. Method embodiments are also disclosed.