A method of fabricating a semiconductor device includes forming a gate pattern on a substrate, and etching sides of the gate pattern using a first wet-etching process to form a first recess. The first wet-etching process includes using an etchant containing a first chemical substance including a hydroxyl functional group (—OH) and a second chemical substance capable of oxidizing the substrate. The concentration of the second chemical substance is 1.5 times or less the concentration of the first chemical substance.