Method of manufacturing semiconductor device having step gates

Abstract

A semiconductor device having step gates includes a semiconductor substrate including first regions having relatively low steps at both ends of an active region defined by trench isolation films and a second region having a relatively high step at a central part of the active region, a groove having a predetermined depth being formed at the central part of the second region, step gate stacks formed on the boundary between the first region and second region while exposing the groove of the second region, first impurity regions formed in the first regions exposed by the step gate stacks, and a second impurity region formed in the second region exposed by the step gate stacks while enclosing the groove of the second region.

1 . A method of manufacturing a semiconductor device having step gates, the method comprising:
 forming trench isolation films on a semiconductor substrate using hard mask film patterns covering an active region thereof;   removing a portion of the hard mask film patterns to expose a first surface and second surface of the active region, while allowing the first and second surfaces to be separated by the hard mask film patterns formed at a central part of the active region;   forming selective epitaxial growth layers on the first and second surfaces of the active region;   removing the hard mask film patterns;   forming step gate stacks on the boundary between the semiconductor substrate of the active region and selective epitaxial growth layer; and   forming first impurity regions and a second impurity region in the semiconductor substrate using the step gate stacks as an ion implantation mask.   
   
   
       2 . The method according to  claim 1 , wherein the selective epitaxial growth layer is grown using dichlorosilane, hydrochloric acid and hydrogen as source gases. 
   
   
       3 . The method according to  claim 1 , further comprising:
 cleaning the exposed first and second surfaces of the active region after exposure thereof.   
   
   
       4 . The method according to  claim 3 , wherein the cleaning process is carried out using at least one of first and second cleansing solutions, the first cleaning solution comprising sulfuric acid and hydrogen peroxide, the second cleaning solution consisting essentially of hydrofluoric acid and ammonium fluoride. 
   
   
       5 . The method according to  claim 4 , wherein the first cleaning solution is a 4:1 mixture of sulfuric acid and hydrogen peroxide. 
   
   
       6 . The method according to  claim 4 , wherein the second cleaning solution is a 300:1 mixture of hydrofluoric acid and ammonium fluoride. 
   
   
       7 . The method according to  claim 1 , further comprising:
 forming bottom electrode films electrically coupled to the first impurity regions, and capacitors including a dielectric film and top electrode film sequentially formed on the bottom electrode films; and   forming a bit line stack coupled to the second impurity region.