Yes, foreign workers may apply for permanent residency after legally residing and working in Switzerland for a certain period. Generally, non-EU/EFTA nationals must live in Switzerland for 10 years before applying for a C permit (permanent residence). However, in some cases, this period may be reduced to 5 years if the applicant demonstrates strong integration, such as proficiency in a national language and stable employment. Holding a work visa or residence permit consistently, complying with tax obligations, and maintaining a clean record are essential prerequisites for progressing to permanent residency.