A semiconductor device is provided. The semiconductor device includes a substrate, a first base fin protruding from the substrate and extending in a first direction, and a first fin type pattern protruding from the first base fin and extending in the first direction. The first base fin includes a first sidewall and a second sidewall, the first and second sidewalls extending in the first direction, the first sidewall opposite to the second sidewall, the first sidewall of the first base fin at least partially defines a first deep trench, the second sidewall of the first base fin at least partially defines a second deep trench, and a depth of the first deep trench is greater than a depth of the second deep trench.