A highly reliable semiconductor device is manufactured by giving stable electric characteristics to a transistor in which an oxide semiconductor film is used. In a transistor using an oxide semiconductor film for an active layer, a microvoid is provided in a source region and a drain region adjacent to a channel region. By providing a microvoid in the source region and the drain region formed in an oxide semiconductor film, hydrogen contained in the channel region of an oxide semiconductor film can be captured in the microvoid.