A semiconductor device including fin type patterns is provided. The semiconductor device includes a first fin type pattern, a field insulation layer disposed in vicinity of the first fin type pattern and having a first part and a second part, the first part protruding from the second part, a first dummy gate stack formed on the first part of the field insulation layer and including a first dummy gate insulation layer having a first thickness, and a first gate stack formed on the second part of the field insulation layer to intersect the first fin type pattern and including a first gate insulation layer having a second thickness different from the first thickness.