Substrate processing apparatus and manufacturing method of substrate holding unit

A substrate processing apparatus configured to perform a preset processing on a processing target substrate and a support substrate, the substrate processing apparatus comprising:

• a first holding unit configured to hold the processing target substrate;
• a second holding unit disposed to face the first holding unit and configured to hold the support substrate by electrostatically attracting the support substrate;
• and
• an ultraviolet irradiation unit configured to irradiate an ultraviolet ray to an ultraviolet curing material provided between the processing target substrate held by the first holding unit and the support substrate held by the second holding unit,
• wherein each of the support substrate and the second holding unit is made of a material through which the ultraviolet ray is transmitted,
• an electrode configured to electrostatically attract the support substrate is provided within the second holding unit, and
• a diffusion layer configured to diffuse a transmission direction of the ultraviolet ray is provided at a position closer to the support substrate between the support substrate and the electrode within the second holding unit.