Semiconductor device

Abstract

Disclosed is a semiconductor device with a transistor in which an oxide semiconductor is used. An insulating layer on a back channel side of the oxide semiconductor layer has capacitance of lower than or equal to 1.5×10 −10 F/m 2 . For example, in the case of a top-gate transistor, a base insulating layer has capacitance of lower than or equal to 1.5×10 −10 F/m 2 , whereby the adverse effect of an interface state between the substrate and the base insulating layer can be reduced. Thus, a semiconductor device where fluctuation in electrical characteristics is small and reliability is high can be manufactured.

1 . A semiconductor device comprising:
 a substrate;   a gate electrode;   an oxide semiconductor layer;   a source electrode and a drain electrode electrically connected to the oxide semiconductor layer;   a gate insulating layer formed between the gate electrode and the oxide semiconductor layer; and   an insulating layer which faces the gate insulating layer with the oxide semiconductor layer interposed therebetween and which is in contact with the oxide semiconductor layer,   wherein the insulating layer has a thickness in which capacitance per unit area is lower than or equal to 2×10 −4  F/m 2  by capacitance.   
     
     
         2 . The semiconductor device according to  claim 1 , wherein the insulating layer comprises one or more of silicon oxide, silicon nitride, silicon oxynitride, silicon nitride oxide, aluminum oxide, and aluminum nitride. 
     
     
         3 . The semiconductor device according to  claim 1 , wherein the insulating layer comprises multiple layers, wherein one of the multiple layers which is in contact with the oxide semiconductor layer is an oxide layer. 
     
     
         4 . A semiconductor device comprising:
 a substrate;   an insulating layer over the substrate;   an oxide semiconductor layer over and in contact with the insulating layer;   a source electrode and a drain electrode over the insulating layer, wherein the source electrode and the drain electrode are electrically connected to the oxide semiconductor layer;   a gate insulating layer over the oxide semiconductor layer, the source electrode and the drain electrode; and   a gate electrode over the gate insulating layer,   wherein the insulating layer has a thickness in which capacitance per unit area is lower than or equal to 2×10 −4  F/m 2  by capacitance.   
     
     
         5 . The semiconductor device according to  claim 4 , wherein the insulating layer comprises one or more of silicon oxide, silicon nitride, silicon oxynitride, silicon nitride oxide, aluminum oxide, and aluminum nitride. 
     
     
         6 . The semiconductor device according to  claim 4 , wherein the insulating layer comprises multiple layers, wherein one of the multiple layers which is in contact with the oxide semiconductor layer is an oxide layer. 
     
     
         7 . The semiconductor device according to  claim 4 , wherein the source electrode and the drain electrode are formed between the gate insulating layer and the oxide semiconductor layer. 
     
     
         8 . The semiconductor device according to  claim 4 , wherein the source electrode and the drain electrode are formed between the insulating layer and the oxide semiconductor layer. 
     
     
         9 . An electronic device including the semiconductor device according to  claim 4 . 
     
     
         10 . A semiconductor device comprising:
 a substrate;   a gate electrode over the substrate;   a gate insulating layer over the gate electrode;   an oxide semiconductor layer over the gate insulating layer;   a source electrode and a drain electrode over the gate insulating layer, wherein the source electrode and the drain electrode are electrically connected to the oxide semiconductor layer; and   an insulating layer over and in contact with the oxide semiconductor layer,   wherein the insulating layer has a thickness in which capacitance per unit area is lower than or equal to 2×10 −4  F/m 2  by capacitance.   
     
     
         11 . The semiconductor device according to  claim 10 , wherein the insulating layer comprises one or more of silicon oxide, silicon nitride, silicon oxynitride, silicon nitride oxide, aluminum oxide, and aluminum nitride. 
     
     
         12 . The semiconductor device according to  claim 10 , wherein the insulating layer comprises multiple layers, wherein one of the multiple layers which is in contact with the oxide semiconductor layer is an oxide layer. 
     
     
         13 . The semiconductor device according to  claim 10 , wherein the source electrode and the drain electrode are formed between the oxide semiconductor layer and the insulating layer. 
     
     
         14 . The semiconductor device according to  claim 10 , wherein the source electrode and the drain electrode are formed between the gate insulating layer and the oxide semiconductor layer. 
     
     
         15 . An electronic device including the semiconductor device according to  claim 10 . 
     
     
         16 . A semiconductor device comprising:
 a substrate;   an insulating layer over the substrate;   an oxide semiconductor layer over and in contact with the insulating layer, wherein the oxide semiconductor layer includes a source region and a drain region in which a resistance of the oxide semiconductor layer is reduced and a channel region;   a gate insulating layer over the oxide semiconductor layer;   a gate electrode over the gate insulating layer;   a protective insulating layer over the oxide semiconductor layer and the gate electrode; and   a source electrode and a drain electrode electrically connected to the oxide semiconductor layer through the protective insulating layer,   wherein the insulating layer has a thickness in which capacitance per unit area is lower than or equal to 2×10 −4  F/m 2  by capacitance.   
     
     
         17 . The semiconductor device according to  claim 16 , wherein the insulating layer comprises one or more of silicon oxide, silicon nitride, silicon oxynitride, silicon nitride oxide, aluminum oxide, and aluminum nitride. 
     
     
         18 . The semiconductor device according to  claim 16 , wherein the insulating layer comprises multiple layers, wherein one of the multiple layers which is in contact with the oxide semiconductor layer is an oxide layer. 
     
     
         19 . An electronic device including the semiconductor device according to  claim 16 .