PURPOSE: To flatten and microminiaturize a semiconductor nonvolatile memory cell by burying a first layer gate insulating film and a floating gate between a source region and a drain region on a semiconductor substrate.

CONSTITUTION: After an oxide film 301 is formed on an Si substrate, a trench structure is formed on a portion to become a gate. Then, the film 301 is re moved, and a side wall 302 is formed by a nitride film. Then, after an oxide film 303 is formed on the overall surface, the wall 302 is separated, and a thin oxide film 304 is further formed. Subsequently, a polysilicon is deposited, and etched to the surface of the substrate to form a floating gate 305. After an oxide film 306 is formed on the entire surface, a control gate 307 is formed, a drain region 308 and a source region 309 are ion implanted to obtain a nonvolatile memory cell. Thus, the cell can be flattened and microminiaturized.