A SOI substrate of high quality which allows LSI to be formed thereon in an improved yield and realizes excellent electric properties and a method for the production thereof are provided. The SOI substrate is obtained by forming an embedded oxide layer on a silicon single crystal substrate and forming a SOI layer for the formation of a device on the embedded oxide layer and is characterized by the SOI layer containing pit-like defects at a density of not more than 5 cm−2 or the embedded oxide layer containing pinhole defects at a density of less than one piece/cm2.