Nonvolatile semiconductor memory device having floating gate that includes two layers
First Claim
1. A nonvolatile semiconductor memory device comprising:
- a substrate;
a base insulating layer over the substrate;
a semiconductor layer over the base insulating layer, the semiconductor layer including a channel forming region between a first impurity region and a second impurity region which are formed apart from each other;
a first insulating layer over the channel forming region;
a floating gate over the channel forming region with the first insulating layer interposed therebetween;
a second insulating layer over the floating gate; and
a control gate over the floating gate with the second insulating layer interposed therebetween,wherein the floating gate includes at least a first layer which is in direct contact with the first insulating layer and a second layer formed over the first layer,wherein the first layer comprises germanium or a germanium compound, andwherein the second layer is formed of a material selected from the group consisting of a metal, an alloy, and a metal compound which is different from the germanium or the germanium compound.
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Abstract
It is an object to provide a nonvolatile semiconductor memory device with an excellent writing property and charge-retention property. A semiconductor layer including a channel forming region between a pair of impurity regions which are formed to be apart from each other is provided. In an upper layer portion thereof, a first insulating layer, a floating gate electrode, a second insulating layer, and a control gate electrode are provided. The floating gate has at least a two-layer structure, and a first layer being in contact with the first insulating layer preferably has a band gap smaller than that of the semiconductor layer. The stability of the first layer is improved by formation of a second layer of the floating gate electrode using a metal, an alloy, or a metal compound material. Such a structure of the floating gate electrode can improve injectability of carriers in writing and a charge-retention property.
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Citations
40 Claims
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1. A nonvolatile semiconductor memory device comprising:
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a substrate; a base insulating layer over the substrate; a semiconductor layer over the base insulating layer, the semiconductor layer including a channel forming region between a first impurity region and a second impurity region which are formed apart from each other; a first insulating layer over the channel forming region; a floating gate over the channel forming region with the first insulating layer interposed therebetween; a second insulating layer over the floating gate; and a control gate over the floating gate with the second insulating layer interposed therebetween, wherein the floating gate includes at least a first layer which is in direct contact with the first insulating layer and a second layer formed over the first layer, wherein the first layer comprises germanium or a germanium compound, and wherein the second layer is formed of a material selected from the group consisting of a metal, an alloy, and a metal compound which is different from the germanium or the germanium compound. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A nonvolatile semiconductor memory device comprising:
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a substrate; a base insulating layer over the substrate; a semiconductor layer over the base insulating layer, the semiconductor layer including a channel forming region between a first impurity region and a second impurity region which are formed apart from each other; a first insulating layer over the channel forming region; a floating gate over the channel forming region with the first insulating layer interposed therebetween; a second insulating layer over the floating gate; and a control gate over the floating gate with the second insulating layer interposed therebetween, wherein the floating gate includes at least a first layer which is in direct contact with the first insulating layer and a second layer formed over the first layer, wherein the first layer comprises germanium or a germanium compound, wherein the second layer is formed of a material selected from the group consisting of a metal, an alloy, and a metal compound which is different from the germanium and the germanium compound, and wherein the germanium compound is germanium oxide or germanium nitride. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A nonvolatile semiconductor memory device comprising:
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a substrate; a base insulating layer over the substrate; an island-like semiconductor layer over the base insulating layer, the island-like semiconductor layer including a channel forming region between a first impurity region and a second impurity region which are formed apart from each other; a first insulating layer over the channel forming region; a floating gate over the channel forming region with the first insulating layer interposed therebetween; a second insulating layer over the floating gate; and a control gate over the floating gate with the second insulating layer interposed therebetween, wherein the floating gate includes at least a first layer which is in direct contact with the first insulating layer and a second layer formed over the first layer, wherein the first layer comprises germanium or a germanium compound, wherein the second layer is formed of a material selected from the group consisting of a metal, an alloy, and a metal compound which is different from the germanium and the germanium compound, and wherein a plurality of the floating gates and the control gates are arranged over the island-like semiconductor layer, each control gate being stacked over the floating gate. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
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Specification