A process for fabricating a MONOS device having a buried bit-line includes providing a semiconductor substrate and forming a mask layer overlying the semiconductor substrate. Thereafter, an etch process is performed to form a trench in the semiconductor substrate. Next, the mask layer is removed and the trench in the semiconductor substrate is filled with a silicon oxide layer. To form a bit-line oxide layer, a planarization process is utilized to planarize the silicon oxide layer and form a planar surface continuous with an upper surface of the semiconductor substrate.