YBa2Cu3O7<FONT FACE=Symbol>-</FONT>d thin films were deposited on MgO single crystals by means of an eclipse pulsed laser deposition method. Deposited films are cooled down in situ under an oxygen atmosphere at a given oxygen pressure. The relationship between critical temperature and oxygen deficiency was investigated by means of electrical resistance R(T) and x-ray diffraction measurements. Post-deposition cooling is critical and the high pressure of oxygen during cooling is favorable.