A complex dry vacuum pump including a root rotor and a screw rotor is disclosed for manufacturing semiconductors and/or displays in a vacuum state in a process chamber, and discharging gaseous material and/or by-products generated during manufacturing to the exterior of the process chamber. The pump can provide high gas compression transfer efficiency so as to form a vacuum in the process chamber and/or keep high gas compression transfer efficiency when the gaseous material and/or by-products are discharged. Balance between the root rotor and the screw rotor can prevent vibration and noise generated in the vacuum pump, and molding material associated with the pump may allow a stator coil to be separated and prevent various by-products from flowing from the vacuum pump.