Semiconductor device and method of fabricating the same

A semiconductor device, comprising:

• a substrate;
• a device isolation layer in the substrate to define an active region;
• a channel layer on the active region;
• a gate electrode on the channel layer;
• and
• source/drain regions in the active region at both sides of the gate electrode,
• the device isolation layer including:
• a first insulating layer;
• a second insulating layer conformally covering the first insulating layer;
• and
• a third insulating layer on the second insulating layer,
• a portion of an upper portion of the second insulating layer being exposed by the first and third insulating layers.

A method of fabricating a semiconductor device, the method comprising:

• forming a device isolation layer in a substrate including a first region, a second region, and a third region;
• forming a first mask layer in the first and third regions to selectively expose the substrate of the second region;
• and
• selectively forming a channel layer on the substrate of the second region.