Semiconductor device with STI and method for manufacturing the semiconductor device
A semiconductor device includes: a semiconductor substrate having first and second areas; an STI isolation region being made of an isolation trench formed in the semiconductor substrate and an insulating film burying the isolation trench and defining a plurality of active regions in the first and second areas; a first structure formed on an area from the active region in the first area to a nearby STI isolation region and having a first height; and a second structure formed on an area from the active region in the second area to a nearby STI isolation region and having a second height, wherein the surface of the said STI isolation region in the first area is lower than the surface of said STI isolation region in the second area.
1. A method for manufacturing a semiconductor device comprising:
forming a mask pattern on a semiconductor substrate that includes a memory cell area and a logic circuit area;
forming an isolation trench, that defines a first active region of the semiconductor substrate in the memory cell area and a second active region of the semiconductor substrate in the logic circuit area, in the semiconductor substrate, the mask pattern being located on the first active region and the second active region;
forming an isolation material film in the isolation trench;
forming a resist pattern that covers the isolation material film in the logic circuit area;
implanting ions to the first active region using the resist pattern as a mask;
removing part of the isolation material film in the memory cell area using the resist pattern as a mask; and
removing the resist pattern and the mask pattern after the implanting ions and the removing part of the isolation material film.
2. The method for manufacturing a semiconductor device according to claim 1 ,
wherein the forming the isolation trench is performed using the mask pattern as a mask.
3. The method for manufacturing a semiconductor device according to claim 2 , wherein the forming the isolation trench is performed by dry etching using the mask pattern as a mask.
4. The method for manufacturing a semiconductor device according to claim 1 , wherein in area subjected to the removing part of the isolation material film, the isolation material film in the memory cell area remains and becomes thinner than the isolation material film in the logic circuit area.
5. The method for manufacturing a semiconductor device according to claim 1 , wherein the mask pattern includes silicon nitride.
6. The method for manufacturing a semiconductor device according to claim 1 , wherein the implanting ions to the first active region is done through the mask pattern.