Semiconductor device and method for manufacturing the same

Abstract

An embodiment is to include an inverted staggered (bottom gate structure) thin film transistor in which an oxide semiconductor film containing In, Ga, and Zn is used as a semiconductor layer and a buffer layer is provided between the semiconductor layer and a source and drain electrode layers. The buffer layer having higher carrier concentration than the semiconductor layer is provided intentionally between the source and drain electrode layers and the semiconductor layer, whereby an ohmic contact is formed.

1 . (canceled) 
     
     
         2 . A semiconductor device comprising:
 an oxide semiconductor film comprising indium and oxygen, the oxide semiconductor film comprising a channel formation region;   a first conductive film over and electrically connected to the oxide semiconductor film; and   a second conductive film over and electrically connected to the oxide semiconductor film,   wherein the oxide semiconductor film comprises an end portion, a groove portion, and a portion between the groove portion and the end portion,   wherein a thickness of the portion is larger than a thickness of the groove portion and larger than a thickness of the end portion, and   wherein the oxide semiconductor film extends beyond a side edge of one of the first conductive film and the second conductive film, the extended portion of the oxide semiconductor film being the end portion.   
     
     
         3 . The semiconductor device according to  claim 2 , wherein the oxide semiconductor film has a carrier concentration lower than 1×10 17  atoms/cm 3 . 
     
     
         4 . The semiconductor device according to  claim 2 , wherein the oxide semiconductor film comprises an In—Ga—Zn—O-based oxide semiconductor. 
     
     
         5 . An electronic appliance comprising the semiconductor device according to  claim 2 , wherein the electronic appliance is configured to read a program or data stored in a recording medium to display it on a display portion. 
     
     
         6 . A semiconductor device comprising:
 an oxide semiconductor film comprising indium and oxygen, the oxide semiconductor film comprising a channel formation region;   a first conductive film electrically connected to the oxide semiconductor film with a first film comprising oxide interposed therebetween; and   a second conductive film electrically connected to the oxide semiconductor film with a second film comprising oxide interposed therebetween,   wherein the oxide semiconductor film comprises an end portion, a groove portion, and a portion between the groove portion and the end portion,   wherein a thickness of the portion is larger than a thickness of the groove portion and larger than a thickness of the end portion, and   wherein the oxide semiconductor film extends beyond a side edge of one of the first film and the second film, the extended portion of the oxide semiconductor film being the end portion.   
     
     
         7 . The semiconductor device according to  claim 6 ,
 wherein the first film is not in contact with a top surface of the end portion, and   wherein the second film is not in contact with a top surface of the end portion.   
     
     
         8 . The semiconductor device according to  claim 6 , wherein each of the first film and the second film comprises In, Ga, and Zn. 
     
     
         9 . The semiconductor device according to  claim 6 , wherein each of the first film and the second film comprises magnesium, aluminum, titanium, iron, tin, calcium, germanium, scandium, yttrium, zirconium, hafnium, boron, thallium, or lead. 
     
     
         10 . The semiconductor device according to  claim 6 , wherein the oxide semiconductor film comprises an In—Ga—Zn—O-based oxide semiconductor. 
     
     
         11 . An electronic appliance comprising the semiconductor device according to  claim 6 , wherein the electronic appliance is configured to read a program or data stored in a recording medium to display it on a display portion. 
     
     
         12 . A semiconductor device comprising:
 an oxide semiconductor film comprising indium and oxygen, the oxide semiconductor film comprising a channel formation region;   a first copper film electrically connected to the oxide semiconductor film with a first film comprising oxide interposed therebetween; and   a second copper film electrically connected to the oxide semiconductor film with a second film comprising oxide interposed therebetween,   wherein the oxide semiconductor film comprises an end portion, a groove portion, and a portion between the groove portion and the end portion,   wherein a thickness of the portion is larger than a thickness of the groove portion and larger than a thickness of the end portion,   wherein the oxide semiconductor film extends beyond a side edge of one of the first film and the second film, the extended portion of the oxide semiconductor film being the end portion,   wherein a first gap between the first film and the second film is smaller than a second gap between the first copper film and the second copper film, and   wherein the first gap is a distance between an upper end portion of the first film and an upper end portion of the second film, and the second gap is a distance between a lower end portion of the first copper film and a lower end portion of second copper film.   
     
     
         13 . The semiconductor device according to  claim 12 ,
 wherein the first film is not in contact with a top surface of the end portion, and   wherein the second film is not in contact with a top surface of the end portion.   
     
     
         14 . The semiconductor device according to  claim 12 , wherein each of the first film and the second film comprises In, Ga, and Zn. 
     
     
         15 . The semiconductor device according to  claim 12 , wherein each of the first film and the second film comprises magnesium, aluminum, titanium, iron, tin, calcium, germanium, scandium, yttrium, zirconium, hafnium, boron, thallium, or lead. 
     
     
         16 . The semiconductor device according to  claim 12 , wherein the oxide semiconductor film comprises an In—Ga—Zn—O-based oxide semiconductor. 
     
     
         17 . An electronic appliance comprising the semiconductor device according to  claim 12 , wherein the electronic appliance is configured to read a program or data stored in a recording medium to display it on a display portion. 
     
     
         18 . A semiconductor device comprising:
 an oxide semiconductor film comprising indium and oxygen, the oxide semiconductor film comprising a channel formation region;   a first copper film electrically connected to the oxide semiconductor film with a first film comprising oxide interposed therebetween; and   a second copper film electrically connected to the oxide semiconductor film with a second film comprising oxide interposed therebetween,   wherein the oxide semiconductor film comprises an end portion, a groove portion, and a portion between the groove portion and the end portion,   wherein a thickness of the portion is larger than a thickness of the groove portion and larger than a thickness of the end portion,   wherein the oxide semiconductor film extends beyond a side edge of one of the first film and the second film, the extended portion of the oxide semiconductor film being the end portion,   wherein a first gap between the first film and the second film is smaller than a second gap between the first copper film and the second copper film,   wherein the first gap is a distance between an upper end portion of the first film and an upper end portion of the second film, and the second gap is a distance between a lower end portion of the first copper film and a lower end portion of second copper film, and   wherein the oxide semiconductor film has a carrier concentration lower than 1×10 17  atoms/cm 3 .   
     
     
         19 . The semiconductor device according to  claim 18 ,
 wherein the first film is not in contact with a top surface of the end portion, and   wherein the second film is not in contact with a top surface of the end portion.   
     
     
         20 . The semiconductor device according to  claim 18 , wherein each of the first film and the second film comprises In, Ga, and Zn. 
     
     
         21 . The semiconductor device according to  claim 18 , wherein each of the first film and the second film comprises magnesium, aluminum, titanium, iron, tin, calcium, germanium, scandium, yttrium, zirconium, hafnium, boron, thallium, or lead. 
     
     
         22 . The semiconductor device according to  claim 18 , wherein the oxide semiconductor film comprises an In—Ga—Zn—O-based oxide semiconductor. 
     
     
         23 . An electronic appliance comprising the semiconductor device according to  claim 18 , wherein the electronic appliance is configured to read a program or data stored in a recording medium to display it on a display portion.