Semiconductor Device and Manufacturing Method Thereof

Abstract

A minute transistor is provided. A transistor with low parasitic capacitance is provided. A transistor having high frequency characteristics is provided. A semiconductor device including the transistor is provided. The semiconductor device includes an oxide semiconductor; a second insulator; a first conductor and a first insulator that are embedded in the second insulator; a second conductor; a third conductor; and a third insulator covering the oxide semiconductor. The oxide semiconductor includes a region where an angle formed between a plane that is parallel to a bottom surface of the oxide semiconductor and the side surface of the oxide semiconductor is greater than or equal to 30° and less than or equal to 60°.

1 - 9 . (canceled) 
     
     
         10 . A method for manufacturing a semiconductor device comprising the steps of:
 forming a second insulator over a first insulator;   forming an oxide semiconductor over the second insulator;   forming a first conductor over the oxide semiconductor;   forming a first resist mask over the first conductor by a lithography method;   etching the first conductor using the first resist mask as an etching mask;   etching the oxide semiconductor and the second insulator using the first resist mask and the first conductor as etching masks so that the oxide semiconductor and the second insulator comprise regions where a taper angle of the oxide semiconductor and a taper angle of the second insulator are each greater than or equal to 30° and less than or equal to 60°;   removing the first resist mask and the first conductor;   forming a third insulator over the first insulator, the second insulator, and the oxide semiconductor;   performing treatment using plasma comprising oxygen on the third insulator, so that oxygen in the plasma is added to the third insulator as excess oxygen;   performing heat treatment, so that the excess oxygen in the third insulator moves to the oxide semiconductor;   forming a second conductor over the third insulator;   forming a second resist mask over the second conductor by a lithography method;   etching the second conductor and the third insulator using the second resist mask as an etching mask;   forming a fourth insulator over the first insulator and the second conductor;   forming, in the fourth insulator, an opening that exposes the second conductor;   forming, in the second conductor, an opening that exposes the third insulator, so that the second conductor is divided into a first conductor layer and a second conductor layer;   forming a fifth insulator over the fourth insulator and the third insulator;   forming a third conductor over the fifth insulator; and   polishing the third conductor and the fifth insulator, so that the fourth insulator is exposed,   wherein the second insulator and the third insulator comprise at least one of main component elements of the oxide semiconductor other than oxygen.   
     
     
         11 . The method for manufacturing the semiconductor device according to  claim 10 , wherein a distance between an end portion of the first conductor layer and an end portion of the second conductor layer that face each other is greater than or equal to 5 nm and less than or equal to 80 nm. 
     
     
         12 . The method for manufacturing the semiconductor device according to  claim 10 , wherein the oxide semiconductor comprises a region where an angle formed between a plane that is parallel to a bottom surface of the oxide semiconductor and the side surface of the oxide semiconductor is greater than or equal to 30° and less than or equal to 60°. 
     
     
         13 . The method for manufacturing the semiconductor device according to  claim 10 , wherein the second conductor comprises a first layer and a second layer over the first layer, and wherein the second layer is less likely to transmit oxygen than the first layer.