Method of fabricating nonvolatile semiconductor memory device
First Claim
1. A method for fabricating a nonvolatile semiconductor memory device, comprising:
- a first step of forming a gate structure on a semiconductor substrate, the gate structure comprising a tunnel insulation film being in contact with the semiconductor substrate, a floating gate electrode being in contact with the tunnel insulation film, a control gate electrode facing the floating gate with an intervening capacitive insulation film;
a second step of forming ion injection adjustment films comprising an insulation film being in contact with the floating gate electrode at least on side surfaces of the floating gate electrode;
a third step of injecting an impurity ion into active regions beside the gate structure in the semiconductor substrate by using the gate structure and the ion injection adjustment film as masks; and
a fourth step of thermally diffusing the injected impurity ion by performing heat treatment on the active regions;
wherein, in the second step, the film thickness of the ion injection adjustment film is chosen so as to prevent the impurity ion from being injected into the tunnel insulation film and to allow the impurity ion to reach a portion below a side end portion of the floating gate electrode in the active regions as a result of diffusive scattering of the impurity ion into the semiconductor substrate.
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Accused Products
Abstract
A gate structure composed of a tunnel insulation film, a floating gate electrode, a capacitive insulation film and a control gate electrode is formed on a semiconductor substrate. Then, ion injection adjustment films that are in contact with the floating gate electrode at least on the side surfaces of the floating gate electrode are formed. After injecting impurity ions into the active region beside the gate structure in the semiconductor substrate while using the gate structure and the ion injection adjustment film as masks, the injected impurity ions are diffused thermally by performing heat treatment on the active region. Film thickness of the ion injection adjustment film is selected to a value to prevent the impurity ions from being injected into the tunnel insulation film and allows the impurity ions to reach lower portions of side end of the floating gate electrode in the active region as a result of diffusive scattering of impurity ions in the semiconductor substrate.
18 Citations
17 Claims
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1. A method for fabricating a nonvolatile semiconductor memory device, comprising:
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a first step of forming a gate structure on a semiconductor substrate, the gate structure comprising a tunnel insulation film being in contact with the semiconductor substrate, a floating gate electrode being in contact with the tunnel insulation film, a control gate electrode facing the floating gate with an intervening capacitive insulation film;
a second step of forming ion injection adjustment films comprising an insulation film being in contact with the floating gate electrode at least on side surfaces of the floating gate electrode;
a third step of injecting an impurity ion into active regions beside the gate structure in the semiconductor substrate by using the gate structure and the ion injection adjustment film as masks; and
a fourth step of thermally diffusing the injected impurity ion by performing heat treatment on the active regions;
wherein, in the second step, the film thickness of the ion injection adjustment film is chosen so as to prevent the impurity ion from being injected into the tunnel insulation film and to allow the impurity ion to reach a portion below a side end portion of the floating gate electrode in the active regions as a result of diffusive scattering of the impurity ion into the semiconductor substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification