A semiconductor device operating at low voltage is provided where a threshold voltage is controlled with ease. A semiconductor substrate is element-isolated by element isolation regions. A source region and a source region are spaced from each other on the semiconductor substrate. A gate electrode is formed between the source region and the drain by way of a gate insulator. A plurality of insulating particles are embedded in the gate electrode in a scattered manner at an interface between the gate insulator and the gate electrode, where the particles are in contact with the gate insulator.