| 摘要 |
PURPOSE: A method of a making a MOS transistor with double gates is provided to form a field oxide layer of a trench and an insulation film and to shape a upper gate and a contact plug while preventing a crack on gate oxide layer. CONSTITUTION: A method comprises the steps: forming on a first conductive substrate, a gate insulation film, a bottom gate, and a MOS element with an impurity diffusion area; forming on the substrate a trench defining an activated area and a field area; forming insulation film in a determined width on the substrate, the insulation film being in same position with an upper surface of the bottom gate; removing a predetermined portion of the insulation film and forming a contact hole so as to expose a portion of the impurity diffusion area; forming a conductive layer on the insulation film so as to bury the contact hole; and patterning the conductive layer to form the upper gate on the bottom gate and forming a contact pad on the contact hole concurrently. Thereby, it is possible to prevent a damage of the gate oxide and also to simplify the processing by forming the field oxide and an inter-layer insulation film concurrently.
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