Semiconductor device having a buffer structure

Abstract

A semiconductor device includes active regions defined by a device isolation region in a substrate; trenches extending in a first direction to intersect the active regions; buried gate structures buried in the trenches, respectively, and having upper surfaces located on a level lower than a level of upper surfaces of the active regions; a buffer structure covering the active regions, the isolation region, and the buried gate structures; bit line structures extending in a second direction intersecting the first direction on the active regions and connected to the active regions; storage node contacts between the bit line structures, penetrating through the buffer structure and in contact with the active regions; and capacitor structures in contact with an upper surface of the storage node contacts.