Kelly Clarkson's home is apparently becoming a magnet for unwanted visitors ... she's asking a judge for court-ordered protection from a man she claims recently showed up multiple times at her place ... even pulling up in a semi-truck.

According to legal docs, obtained by TMZ, the "American Idol" winner is requesting a temporary restraining order against a man named Victor Fernandez ... and Kelly also wants her family, nanny and house manager protected.

The singer's head of security, Michael Lopez, says Fernandez first showed up at Kelly's home on Thanksgiving, pulling up in a semi-truck and peering over her privacy gate and into her yard. Lopez claims Fernandez returned two more times on Thanksgiving, once in the semi-truck and later on foot, ringing the doorbell and claiming he was there to see Kelly.

In the docs, filed by Kelly's attorney, Ed McPherson, Lopez claims Fernandez came to the house on foot again on Dec. 3, speaking to house staff and telling them Kelly told him to meet her there, even though she says she doesn't have a clue who he is.

Another member of Kelly's security team, Ludwin Munoz, claims he spoke with Fernandez through the home's camera system during the December visit. Munoz claims Fernandez appeared irritated and confused when denied entry, allegedly saying, "This is the second time she has done this ... unless I am speaking to a scammer or something."

Kelly's security also claims Fernandez snapped photos of the family SUV when her nanny pulled up with her children in tow ... and the docs say police were ultimately called and took a report.

The singer's asking a judge to keep Fernandez at least 100 yards away from her home, job, car and her children's school and child care ... and Kelly says she's afraid of what Fernandez might do and fears he may cause harm to her or her family.

TMZ broke the story ... Kelly recently got a different TRO against a woman she claimed made at least 18 unwanted visits to her home.