The present disclosure provides in some aspects a semiconductor device and a method of forming a semiconductor device. According to some illustrative embodiments herein, the semiconductor device includes an active region formed in a semiconductor substrate, a gate structure disposed over the active region, source/drain regions formed in the active region in alignment with the gate structure, and an insulating material region buried into the active region under the gate structure, wherein the insulating material region is surrounded by the active region and borders a channel region in the active region below the gate structure along a depth direction of the active region.