A semiconductor device includes a substrate having a first memory cell and a second memory cell, the first and second memory cells being adjacent to each other in a first direction, first to fourth memory fins adjacent to each other in the first direction in the first memory cell, the first to fourth memory fins protruding from the substrate, fifth to eighth memory fins adjacent to each other in the first direction in the second memory cell, the fifth to eighth memory fins protruding from the substrate, and a first shallow device isolation layer between the fourth memory fin and the fifth memory fin, a sidewall of the first shallow device isolation layer having an inflection point.